openvswitch: checking wrong variable in queue_userspace_packet()

"skb" is non-NULL here, for example we dereference it in skb_clone().
The intent was to test "nskb" which was just set.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/datapath.c

@@ -321,7 +321,7 @@ static int queue_userspace_packet(int dp_ifindex, struct sk_buff *skb,
 			return -ENOMEM;
 
 		nskb = __vlan_put_tag(nskb, vlan_tx_tag_get(nskb));
-		if (!skb)
+		if (!nskb)
 			return -ENOMEM;
 
 		nskb->vlan_tci = 0;