gso: Handle Trans-Ether-Bridging protocol in skb_network_protocol()

Rather than having logic to calculate inner protocol in every
tunnel gso handler move it to gso code. This simplifies code.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Cong Wang <amwang@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
index cc22363..b2e805a 100644
--- a/net/ipv4/gre.c
+++ b/net/ipv4/gre.c
@@ -150,13 +150,7 @@
 		csum = false;
 
 	/* setup inner skb. */
-	if (greh->protocol == htons(ETH_P_TEB)) {
-		struct ethhdr *eth = (struct ethhdr *)skb_inner_mac_header(skb);
-		skb->protocol = eth->h_proto;
-	} else {
-		skb->protocol = greh->protocol;
-	}
-
+	skb->protocol = greh->protocol;
 	skb->encapsulation = 0;
 
 	if (unlikely(!pskb_may_pull(skb, ghl)))