vlan: introduce *vlan_hwaccel_push_inside helpers

Use them to push skb->vlan_tci into the payload and avoid code
duplication.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 65d3723..e0ad5d1 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -79,8 +79,7 @@
 
 	if (vlan_tx_tag_present(skb) &&
 	    !vlan_hw_offload_capable(features, skb->vlan_proto)) {
-		skb = vlan_insert_tag_set_proto(skb, skb->vlan_proto,
-						vlan_tx_tag_get(skb));
+		skb = __vlan_hwaccel_push_inside(skb);
 		if (unlikely(!skb)) {
 			/* This is actually a packet drop, but we
 			 * don't want the code that calls this
@@ -88,7 +87,6 @@
 			 */
 			goto out;
 		}
-		skb->vlan_tci = 0;
 	}
 
 	status = netdev_start_xmit(skb, dev, txq, false);