There is no access to chan->sk in L2CAP core now. This change marks the
end of the task of splitting L2CAP between Core and Socket, thus sk is now
gone from struct l2cap_chan.
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>