openvswitch: make skb->csum consistent with rest of networking stack.

Following patch keeps skb->csum correct across ovs.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 894b6cb..596d637 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -130,9 +130,13 @@
 	if (unlikely(err))
 		return err;
 
+	skb_postpull_rcsum(skb, eth_hdr(skb), ETH_ALEN * 2);
+
 	memcpy(eth_hdr(skb)->h_source, eth_key->eth_src, ETH_ALEN);
 	memcpy(eth_hdr(skb)->h_dest, eth_key->eth_dst, ETH_ALEN);
 
+	ovs_skb_postpush_rcsum(skb, eth_hdr(skb), ETH_ALEN * 2);
+
 	return 0;
 }