net: sch: api: add extack support in qdisc_create_dflt

This patch adds extack support for the function qdisc_create_dflt which is
a common used function in the tc subsystem. Callers which are interested
in the receiving error can assign extack to get a more detailed
information why qdisc_create_dflt failed. The function qdisc_create_dflt
will also call an init callback which can fail by any per-qdisc specific
handling.

Cc: David Ahern <dsahern@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_mq.c b/net/sched/sch_mq.c
index 50292e4..f062a18 100644
--- a/net/sched/sch_mq.c
+++ b/net/sched/sch_mq.c
@@ -61,7 +61,8 @@
 		dev_queue = netdev_get_tx_queue(dev, ntx);
 		qdisc = qdisc_create_dflt(dev_queue, get_default_qdisc_ops(dev, ntx),
 					  TC_H_MAKE(TC_H_MAJ(sch->handle),
-						    TC_H_MIN(ntx + 1)));
+						    TC_H_MIN(ntx + 1)),
+					  extack);
 		if (!qdisc)
 			return -ENOMEM;
 		priv->qdiscs[ntx] = qdisc;