Bluetooth: Fix lookup of fixed channels by local bdaddr

The comparing of chan->src should always be done against the local
identity address, represented by hcon->src and hcon->src_type. This
patch modifies l2cap_global_fixed_chan() to take the full hci_conn so
that we can easily compare against hcon->src and hcon->src_type.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>