[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/drivers/net/myri10ge/myri10ge.c b/drivers/net/myri10ge/myri10ge.c
index f4c8fd3..ee1de97 100644
--- a/drivers/net/myri10ge/myri10ge.c
+++ b/drivers/net/myri10ge/myri10ge.c
@@ -2116,7 +2116,7 @@
 		}
 		idx = (idx + 1) & tx->mask;
 	} while (idx != last_idx);
-	if (skb_shinfo(skb)->gso_size) {
+	if (skb_is_gso(skb)) {
 		printk(KERN_ERR
 		       "myri10ge: %s: TSO but wanted to linearize?!?!?\n",
 		       mgp->dev->name);