net: sock_dequeue_err_skb() optimization

Exit early if the list is empty.

Some applications using TCP zerocopy are calling
recvmsg( ... MSG_ERRQUEUE) and hit this case quite often,
probably because busy polling only deals with sk_receive_queue.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231005114504.642589-1-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>