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_hfsc.c b/net/sched/sch_hfsc.c
index 069c62b..2e45791 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1599,10 +1599,8 @@
 	if (cl->qdisc->q.qlen == 1)
 		set_active(cl, qdisc_pkt_len(skb));
 
-	cl->bstats.packets++;
-	cl->bstats.bytes += qdisc_pkt_len(skb);
-	sch->bstats.packets++;
-	sch->bstats.bytes += qdisc_pkt_len(skb);
+	bstats_update(&cl->bstats, skb);
+	qdisc_bstats_update(sch, skb);
 	sch->q.qlen++;
 
 	return NET_XMIT_SUCCESS;