net/sched: sch_taprio: ensure to reset/destroy all child qdiscs

net/sched: sch_taprio: ensure to reset/destroy all child qdiscs

taprio_graft() can insert a NULL element in the array of child qdiscs. As
a consquence, taprio_reset() might not reset child qdiscs completely, and
taprio_destroy() might leak resources. Fix it by ensuring that loops that
iterate over q->qdiscs[] don't end when they find the first NULL item.

Fixes: c70e77c38821 ("net/sched: sch_taprio: reset child qdiscs before freeing them")
Fixes: 55fb5b5af7a0 ("tc: Add support for configuring the taprio scheduler")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/13edef6778fef03adc751582562fba4a13e06d6a.1608240532.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>