Bluetooth: Fix mgmt interaction with userspace

Partially revert 34918cd7. struct mgmt_key_info needs to have the same
size as its version exported to userspace.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

include/net/bluetooth/mgmt.h

@@ -101,8 +101,6 @@ struct mgmt_key_info {
 	u8 type;
 	u8 val[16];
 	u8 pin_len;
-	u8 dlen;
-	u8 data[0];
 } __packed;
 
 #define MGMT_OP_LOAD_KEYS		0x000D