[INET]: Remove struct dst_entry *dst from request_sock_ops.rtx_syn_ack.

It looks like dst parameter is used in this API due to historical
reasons.  Actually, it is really used in the direct call to
tcp_v4_send_synack only.  So, create a wrapper for tcp_v4_send_synack
and remove dst from rtx_syn_ack.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 027d181..33ad483 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -216,7 +216,7 @@
 			 * counter (backoff, monitored by dccp_response_timer).
 			 */
 			req->retrans++;
-			req->rsk_ops->rtx_syn_ack(sk, req, NULL);
+			req->rsk_ops->rtx_syn_ack(sk, req);
 		}
 		/* Network Duplicate, discard packet */
 		return NULL;