net: sched: implement qstat helper routines

This adds helpers to manipulate qstats logic and replaces locations
that touch the counters directly. This simplifies future patches
to push qstats onto per cpu counters.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index 7a6243c5..907b12f 100644
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -360,7 +360,7 @@
 	cl = drr_classify(skb, sch, &err);
 	if (cl == NULL) {
 		if (err & __NET_XMIT_BYPASS)
-			sch->qstats.drops++;
+			qdisc_qstats_drop(sch);
 		kfree_skb(skb);
 		return err;
 	}
@@ -369,7 +369,7 @@
 	if (unlikely(err != NET_XMIT_SUCCESS)) {
 		if (net_xmit_drop_count(err)) {
 			cl->qstats.drops++;
-			sch->qstats.drops++;
+			qdisc_qstats_drop(sch);
 		}
 		return err;
 	}