net: factor out skb_mac_gso_segment() from skb_gso_segment()

This function will be used in next GRE_GSO patch. This patch does
not change any functionality. It only exports skb_mac_gso_segment()
function.

[ Use skb_reset_mac_len() -DaveM ]

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9deb672..920361bc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2671,6 +2671,8 @@
 extern int skb_checksum_help(struct sk_buff *skb);
 extern struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
 	netdev_features_t features, bool tx_path);
+extern struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb,
+					  netdev_features_t features);
 
 static inline
 struct sk_buff *skb_gso_segment(struct sk_buff *skb, netdev_features_t features)