net: use kfree_skb_list() from ip_do_fragment()

Just like 46cfd725c3 ("net: use kfree_skb_list() helper in more places").

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_output.c

@@ -693,11 +693,8 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 			return 0;
 		}
 
-		while (frag) {
-			skb = frag->next;
-			kfree_skb(frag);
-			frag = skb;
-		}
+		kfree_skb_list(frag);
+
 		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
 		return err;