Bluetooth: Fix updating Identity Address in L2CAP channels

When we receive a remote identity address during SMP key distribution we
should ensure that any associated L2CAP channel instances get their
address information correspondingly updated (so that e.g. doing
getpeername on associated sockets returns the correct address).

This patch adds a new L2CAP core function l2cap_conn_update_id_addr()
which is used to iterate through all L2CAP channels associated with a
connection and update their address information.

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