openvswitch: actions: use skb_postpull_rcsum when possible

Replace duplicated code by calling skb_postpull_rcsum

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/actions.c

@@ -175,10 +175,7 @@ static int pop_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 	if (unlikely(err))
 		return err;
 
-	if (skb->ip_summed == CHECKSUM_COMPLETE)
-		skb->csum = csum_sub(skb->csum,
-				     csum_partial(skb_mpls_header(skb),
-						  MPLS_HLEN, 0));
+	skb_postpull_rcsum(skb, skb_mpls_header(skb), MPLS_HLEN);
 
 	memmove(skb_mac_header(skb) + MPLS_HLEN, skb_mac_header(skb),
 		skb->mac_len);
@@ -230,9 +227,7 @@ static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
 	if (unlikely(err))
 		return err;
 
-	if (skb->ip_summed == CHECKSUM_COMPLETE)
-		skb->csum = csum_sub(skb->csum, csum_partial(skb->data
-					+ (2 * ETH_ALEN), VLAN_HLEN, 0));
+	skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
 
 	vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
 	*current_tci = vhdr->h_vlan_TCI;