sched: Use __qdisc_drop instead of kfree_skb in sch_prio and sch_qfq

The commit 520ac30f ("net_sched: drop packets after root qdisc lock
is released) made a big change of tc for performance. There are two points
left in sch_prio and sch_qfq which are not changed with that commit. Now
enhance them now with __qdisc_drop.
Signed-off-by: NGao Feng <gfree.wind@vip.163.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_prio.c

@@ -80,7 +80,7 @@ prio_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 
 		if (ret & __NET_XMIT_BYPASS)
 			qdisc_qstats_drop(sch);
-		kfree_skb(skb);
+		__qdisc_drop(skb, to_free);
 		return ret;
 	}
 #endif

net/sched/sch_qfq.c

@@ -1215,7 +1215,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	if (cl == NULL) {
 		if (err & __NET_XMIT_BYPASS)
 			qdisc_qstats_drop(sch);
-		kfree_skb(skb);
+		__qdisc_drop(skb, to_free);
 		return err;
 	}
 	pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);