[NET] gso: Add skb_is_gso

This patch adds the wrapper function skb_is_gso which can be used instead
of directly testing skb_shinfo(skb)->gso_size.  This makes things a little
nicer and allows us to change the primary key for indicating whether an skb
is GSO (if we ever want to do that).

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 8be9f21..6ccd32b 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -35,7 +35,7 @@
 int br_dev_queue_push_xmit(struct sk_buff *skb)
 {
 	/* drop mtu oversized packets except gso */
-	if (packet_length(skb) > skb->dev->mtu && !skb_shinfo(skb)->gso_size)
+	if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
 		kfree_skb(skb);
 	else {
 #ifdef CONFIG_BRIDGE_NETFILTER