T99W651 is a RNDIS based modem device. There are 3 serial ports
need to be enumerated: Diag, NMEA and AT.

Test evidence as below:
T:  Bus=01 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#=  6 Spd=480 MxCh= 0
D:  Ver= 2.10 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=0489 ProdID=e145 Rev=05.15
S:  Manufacturer=QCOM
S:  Product=SDXPINN-IDP _SN:93B562B2
S:  SerialNumber=82e6fe26
C:  #Ifs= 7 Cfg#= 1 Atr=a0 MxPwr=500mA
I:  If#=0x0 Alt= 0 #EPs= 1 Cls=ef(misc ) Sub=04 Prot=01 Driver=rndis_host
I:  If#=0x1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=rndis_host
I:  If#=0x2 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=40 Driver=option
I:  If#=0x3 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=40 Driver=option
I:  If#=0x4 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=30 Driver=option
I:  If#=0x5 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=70 Driver=(none)
I:  If#=0x6 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=42 Prot=01 Driver=(none)

0&1: RNDIS, 2:AT, 3:NMEA, 4:DIAG, 5:QDSS, 6:ADB
QDSS is not a serial port.
Signed-off-by: Slark Xiao <slark_xiao@163.com>
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>