Bluetooth: ISO: unlock on error path in iso_sock_setsockopt()

Call release_sock(sk); before returning on this error path.

Fixes: ccf74f23 ("Bluetooth: Add BTPROTO_ISO socket type")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>