[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/include/linux/skbuff.h b/include/linux/skbuff.h
index 3597b4f..0bf31b8 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1455,5 +1455,10 @@
 { }
 #endif
 
+static inline int skb_is_gso(const struct sk_buff *skb)
+{
+	return skb_shinfo(skb)->gso_size;
+}
+
 #endif	/* __KERNEL__ */
 #endif	/* _LINUX_SKBUFF_H */