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_atm.c b/net/sched/sch_atm.c
index 0101766..040212c 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -417,7 +417,7 @@
 	if (ret != NET_XMIT_SUCCESS) {
 drop: __maybe_unused
 		if (net_xmit_drop_count(ret)) {
-			sch->qstats.drops++;
+			qdisc_qstats_drop(sch);
 			if (flow)
 				flow->qstats.drops++;
 		}