[NET]: Add sk_stream_wmem_schedule

This patch introduces sk_stream_wmem_schedule as a short-hand for
the sk_forward_alloc checking on egress.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 02fdda6..854f6d0 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -552,8 +552,7 @@
 			tcp_mark_push(tp, skb);
 			goto new_segment;
 		}
-		if (sk->sk_forward_alloc < copy &&
-		    !sk_stream_mem_schedule(sk, copy, 0))
+		if (!sk_stream_wmem_schedule(sk, copy))
 			goto wait_for_memory;
 		
 		if (can_coalesce) {