Bluetooth: Move clean up code and set of SOCK_ZAPPED to l2cap_sock.c

This remove a bit more of socket code from l2cap core, this calls set the
SOCK_ZAPPED and do some clean up depending on the socket state.

Reported-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>