[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/include/net/request_sock.h b/include/net/request_sock.h
index cff4608..040780a 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -31,8 +31,7 @@
 	int		obj_size;
 	struct kmem_cache	*slab;
 	int		(*rtx_syn_ack)(struct sock *sk,
-				       struct request_sock *req,
-				       struct dst_entry *dst);
+				       struct request_sock *req);
 	void		(*send_ack)(struct sk_buff *skb,
 				    struct request_sock *req);
 	void		(*send_reset)(struct sock *sk,