Bluetooth: Host: SSP: Correct BR bonding type

Currently, the bonding type of Authentication
_Requirements parameter is always `Dedicated
Bonding` if the device is pairing initiator.

But if the bonding is performed during
connection setup or channel establishment as
a precursor to accessing a service, the
bonding type should be `General bonding`.

Add a flag BT_CONN_BR_GENERAL_BONDING.
Set the flag if the bonding is performed in
the L2CAP_BR/RFCOMM channel establishment.

Set bonding type depends on the flag when
receiving IO cap request.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>