net_sched: factorize qdisc stats handling

HTB takes into account skb is segmented in stats updates.
Generalize this to all schedulers.

They should use qdisc_bstats_update() helper instead of manipulating
bstats.bytes and bstats.packets

Add bstats_update() helper too for classes that use
gnet_stats_basic_packed fields.

Note : Right now, TCQ_F_CAN_BYPASS shortcurt can be taken only if no
stab is setup on qdisc.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index f10e34a..bce1665 100644
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -63,8 +63,7 @@
 
 	result = tc_classify(skb, p->filter_list, &res);
 
-	sch->bstats.packets++;
-	sch->bstats.bytes += qdisc_pkt_len(skb);
+	qdisc_bstats_update(sch, skb);
 	switch (result) {
 	case TC_ACT_SHOT:
 		result = TC_ACT_SHOT;