net_sched: act: use standard struct list_head

Currently actions are chained by a singly linked list,
therefore it is a bit hard to add and remove a specific
entry. Convert it to struct list_head so that in the
latter patch we can remove an action without finding
its head.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_route.c

@@ -481,6 +481,7 @@ static int route4_change(struct net *net, struct sk_buff *in_skb,
 	if (f == NULL)
 		goto errout;
 
+	tcf_exts_init(&f->exts);
 	err = route4_set_parms(net, tp, base, f, handle, head, tb,
 		tca[TCA_RATE], 1);
 	if (err < 0)