sock_poll_wait: kill the no longer necessary barrier after poll_wait()

Now that poll_wait() provides a full barrier we can remove smp_mb() from
sock_poll_wait().

Also, the poll_does_not_wait() check before poll_wait() just adds the
unnecessary confusion, kill it. poll_wait() does the same "p && p->_qproc"
check.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250107162736.GA18944@redhat.com


Signed-off-by: Christian Brauner <brauner@kernel.org>