pkt_sched: Use qdisc->ops->peek() instead of ->dequeue() & ->requeue()

Use qdisc->ops->peek() instead of ->dequeue() & ->requeue() pair.
After this patch the only remaining user of qdisc->ops->requeue() is
netem_enqueue(). Based on ideas of Herbert Xu, Patrick McHardy and
David S. Miller.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index c1e77da..ddfc408 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -880,28 +880,20 @@
 	 */
 }
 
-/*
- * hack to get length of first packet in queue.
- */
 static unsigned int
 qdisc_peek_len(struct Qdisc *sch)
 {
 	struct sk_buff *skb;
 	unsigned int len;
 
-	skb = sch->dequeue(sch);
+	skb = sch->ops->peek(sch);
 	if (skb == NULL) {
 		if (net_ratelimit())
 			printk("qdisc_peek_len: non work-conserving qdisc ?\n");
 		return 0;
 	}
 	len = qdisc_pkt_len(skb);
-	if (unlikely(sch->ops->requeue(skb, sch) != NET_XMIT_SUCCESS)) {
-		if (net_ratelimit())
-			printk("qdisc_peek_len: failed to requeue\n");
-		qdisc_tree_decrease_qlen(sch, 1);
-		return 0;
-	}
+
 	return len;
 }