net: Fix GSO constants to match NETIF flags

Joseph Gasparakis reported that VXLAN GSO offload stopped working with
i40e device after recent UDP changes. The problem is that the
SKB_GSO_* bits are out of sync with the corresponding NETIF flags. This
patch fixes that. Also, we add BUILD_BUG_ONs in net_gso_ok for several
GSO constants that were missing to avoid the problem in the future.

Reported-by: Joseph Gasparakis <joseph.gasparakis@intel.com>
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5b5cd31..e13ed90 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -338,17 +338,18 @@
 
 	SKB_GSO_GRE = 1 << 6,
 
-	SKB_GSO_IPIP = 1 << 7,
+	SKB_GSO_GRE_CSUM = 1 << 7,
 
-	SKB_GSO_SIT = 1 << 8,
+	SKB_GSO_IPIP = 1 << 8,
 
-	SKB_GSO_UDP_TUNNEL = 1 << 9,
+	SKB_GSO_SIT = 1 << 9,
 
-	SKB_GSO_MPLS = 1 << 10,
+	SKB_GSO_UDP_TUNNEL = 1 << 10,
 
 	SKB_GSO_UDP_TUNNEL_CSUM = 1 << 11,
 
-	SKB_GSO_GRE_CSUM = 1 << 12,
+	SKB_GSO_MPLS = 1 << 12,
+
 };
 
 #if BITS_PER_LONG > 32