netfilter: ipt_REJECT: avoid touching dst ref

We can avoid a pair of atomic ops in ipt_REJECT send_reset()
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NPatrick McHardy <kaber@trash.net>

net/ipv4/netfilter/ipt_REJECT.c

@@ -110,7 +110,7 @@ static void send_reset(struct sk_buff *oldskb, int hook)
 		addr_type = RTN_LOCAL;
 
 	/* ip_route_me_harder expects skb->dst to be set */
-	skb_dst_set(nskb, dst_clone(skb_dst(oldskb)));
+	skb_dst_set_noref(nskb, skb_dst(oldskb));
 
 	if (ip_route_me_harder(nskb, addr_type))
 		goto free_nskb;