According to Core Spec Version 5.2 | Vol 3, Part A 6.1.5,
the incoming L2CAP_ConfigReq should be handled during
OPEN state.

The section below shows the btmon trace when running
L2CAP/COS/CFD/BV-12-C before and after this change.

=== Before ===
...
> ACL Data RX: Handle 256 flags 0x02 dlen 12                #22
      L2CAP: Connection Request (0x02) ident 2 len 4
        PSM: 1 (0x0001)
        Source CID: 65
< ACL Data TX: Handle 256 flags 0x00 dlen 16                #23
      L2CAP: Connection Response (0x03) ident 2 len 8
        Destination CID: 64
        Source CID: 65
        Result: Connection successful (0x0000)
        Status: No further information available (0x0000)
< ACL Data TX: Handle 256 flags 0x00 dlen 12                #24
      L2CAP: Configure Request (0x04) ident 2 len 4
        Destination CID: 65
        Flags: 0x0000
> HCI Event: Number of Completed Packets (0x13) plen 5      #25
        Num handles: 1
        Handle: 256
        Count: 1
> HCI Event: Number of Completed Packets (0x13) plen 5      #26
        Num handles: 1
        Handle: 256
        Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 16                #27
      L2CAP: Configure Request (0x04) ident 3 len 8
        Destination CID: 64
        Flags: 0x0000
        Option: Unknown (0x10) [hint]
        01 00                                            ..
< ACL Data TX: Handle 256 flags 0x00 dlen 18                #28
      L2CAP: Configure Response (0x05) ident 3 len 10
        Source CID: 65
        Flags: 0x0000
        Result: Success (0x0000)
        Option: Maximum Transmission Unit (0x01) [mandatory]
          MTU: 672
> HCI Event: Number of Completed Packets (0x13) plen 5      #29
        Num handles: 1
        Handle: 256
        Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 14                #30
      L2CAP: Configure Response (0x05) ident 2 len 6
        Source CID: 64
        Flags: 0x0000
        Result: Success (0x0000)
> ACL Data RX: Handle 256 flags 0x02 dlen 20                #31
      L2CAP: Configure Request (0x04) ident 3 len 12
        Destination CID: 64
        Flags: 0x0000
        Option: Unknown (0x10) [hint]
        01 00 91 02 11 11                                ......
< ACL Data TX: Handle 256 flags 0x00 dlen 14                #32
      L2CAP: Command Reject (0x01) ident 3 len 6
        Reason: Invalid CID in request (0x0002)
        Destination CID: 64
        Source CID: 65
> HCI Event: Number of Completed Packets (0x13) plen 5      #33
        Num handles: 1
        Handle: 256
        Count: 1
...
=== After ===
...
> ACL Data RX: Handle 256 flags 0x02 dlen 12               #22
      L2CAP: Connection Request (0x02) ident 2 len 4
        PSM: 1 (0x0001)
        Source CID: 65
< ACL Data TX: Handle 256 flags 0x00 dlen 16               #23
      L2CAP: Connection Response (0x03) ident 2 len 8
        Destination CID: 64
        Source CID: 65
        Result: Connection successful (0x0000)
        Status: No further information available (0x0000)
< ACL Data TX: Handle 256 flags 0x00 dlen 12               #24
      L2CAP: Configure Request (0x04) ident 2 len 4
        Destination CID: 65
        Flags: 0x0000
> HCI Event: Number of Completed Packets (0x13) plen 5     #25
        Num handles: 1
        Handle: 256
        Count: 1
> HCI Event: Number of Completed Packets (0x13) plen 5     #26
        Num handles: 1
        Handle: 256
        Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 16               #27
      L2CAP: Configure Request (0x04) ident 3 len 8
        Destination CID: 64
        Flags: 0x0000
        Option: Unknown (0x10) [hint]
        01 00                                            ..
< ACL Data TX: Handle 256 flags 0x00 dlen 18               #28
      L2CAP: Configure Response (0x05) ident 3 len 10
        Source CID: 65
        Flags: 0x0000
        Result: Success (0x0000)
        Option: Maximum Transmission Unit (0x01) [mandatory]
          MTU: 672
> HCI Event: Number of Completed Packets (0x13) plen 5     #29
        Num handles: 1
        Handle: 256
        Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 14               #30
      L2CAP: Configure Response (0x05) ident 2 len 6
        Source CID: 64
        Flags: 0x0000
        Result: Success (0x0000)
> ACL Data RX: Handle 256 flags 0x02 dlen 20               #31
      L2CAP: Configure Request (0x04) ident 3 len 12
        Destination CID: 64
        Flags: 0x0000
        Option: Unknown (0x10) [hint]
        01 00 91 02 11 11                                .....
< ACL Data TX: Handle 256 flags 0x00 dlen 18               #32
      L2CAP: Configure Response (0x05) ident 3 len 10
        Source CID: 65
        Flags: 0x0000
        Result: Success (0x0000)
        Option: Maximum Transmission Unit (0x01) [mandatory]
          MTU: 672
< ACL Data TX: Handle 256 flags 0x00 dlen 12               #33
      L2CAP: Configure Request (0x04) ident 3 len 4
        Destination CID: 65
        Flags: 0x0000
> HCI Event: Number of Completed Packets (0x13) plen 5     #34
        Num handles: 1
        Handle: 256
        Count: 1
> HCI Event: Number of Completed Packets (0x13) plen 5     #35
        Num handles: 1
        Handle: 256
        Count: 1
...
Signed-off-by: Howard Chung <howardchung@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>