inet: makes syn_ack_timeout mandatory

There are two struct request_sock_ops providers, tcp and dccp.

inet_csk_reqsk_queue_prune() can avoid testing syn_ack_timeout being
NULL if we make it non NULL like syn_ack_timeout

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Cc: dccp@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index c12396f..d19f32a 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -555,8 +555,7 @@
 				syn_ack_recalc(req, thresh, max_retries,
 					       queue->rskq_defer_accept,
 					       &expire, &resend);
-				if (req->rsk_ops->syn_ack_timeout)
-					req->rsk_ops->syn_ack_timeout(parent, req);
+				req->rsk_ops->syn_ack_timeout(parent, req);
 				if (!expire &&
 				    (!resend ||
 				     !req->rsk_ops->rtx_syn_ack(parent, req, NULL) ||