gro: Remember number of held packets instead of counting every time

This patch prepares for the move of the same_flow checks out of
dev_gro_receive.  As such we need to remember the number of held
packets since doing a loop just to count them every time is silly.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 864519e..9ee344b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -314,6 +314,9 @@
 	spinlock_t		poll_lock;
 	int			poll_owner;
 #endif
+
+	unsigned int		gro_count;
+
 	struct net_device	*dev;
 	struct list_head	dev_list;
 	struct sk_buff		*gro_list;