net: sch: api: add extack support in qdisc_get_rtab

This patch adds extack support for the function qdisc_get_rtab 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_get_rtab failed.

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_tbf.c b/net/sched/sch_tbf.c
index db6bd23..1ab53ff 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -327,11 +327,13 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
 	qopt = nla_data(tb[TCA_TBF_PARMS]);
 	if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE)
 		qdisc_put_rtab(qdisc_get_rtab(&qopt->rate,
-					      tb[TCA_TBF_RTAB]));
+					      tb[TCA_TBF_RTAB],
+					      NULL));
 
 	if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE)
 			qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate,
-						      tb[TCA_TBF_PTAB]));
+						      tb[TCA_TBF_PTAB],
+						      NULL));
 
 	buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U);
 	mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U);