netfilter: xt_HMARK: Use ip_is_fragment() helper

Use ip_is_fragment() to simpify code.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/xt_HMARK.c

@@ -276,7 +276,7 @@ hmark_pkt_set_htuple_ipv4(const struct sk_buff *skb, struct hmark_tuple *t,
 		return 0;
 
 	/* follow-up fragments don't contain ports, skip all fragments */
-	if (ip->frag_off & htons(IP_MF | IP_OFFSET))
+	if (ip_is_fragment(ip))
 		return 0;
 
 	hmark_set_tuple_ports(skb, (ip->ihl * 4) + nhoff, t, info);