Bluetooth: L2CAP: Handle information request command on BR/EDR

Adds support to handle incoming L2CAP information request from
remote to get local information about 'extended features' and 'fixed
channels'. For now local stack ensures support for L2CAP BR/EDR
signalling channel.

Change-Id: If8c9c9dd041b45a79db5e560394dcd2778176f55
Signed-off-by: Arkadiusz Lichwa <arkadiusz.lichwa@tieto.com>