net: Pass NULL to skb_network_protocol() when we don't care about vlan depth

When we don't care about vlan depth, we could pass NULL instead of the
address of a unused local variable to skb_network_protocol() as a param.
Signed-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -3758,7 +3758,6 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 	int err = -ENOMEM;
 	int i = 0;
 	int pos;
-	int dummy;
 
 	if (list_skb && !list_skb->head_frag && skb_headlen(list_skb) &&
 	    (skb_shinfo(head_skb)->gso_type & SKB_GSO_DODGY)) {
@@ -3780,7 +3779,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 	}
 
 	__skb_push(head_skb, doffset);
-	proto = skb_network_protocol(head_skb, &dummy);
+	proto = skb_network_protocol(head_skb, NULL);
 	if (unlikely(!proto))
 		return ERR_PTR(-EINVAL);