sock: unlock on error in sock_setsockopt()

If copy_from_sockptr() then we need to unlock before returning.

Fixes: d463126e

 ("net: sock: extend SO_TIMESTAMPING for PHC binding")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>