net/sched: taprio: simplify list iteration in taprio_dev_notifier()

net/sched: taprio: simplify list iteration in taprio_dev_notifier()

taprio_dev_notifier() subscribes to netdev state changes in order to
determine whether interfaces which have a taprio root qdisc have changed
their link speed, so the internal calculations can be adapted properly.

The 'qdev' temporary variable serves no purpose, because we just use it
only once, and can just as well use qdisc_dev(q->root) directly (or the
"dev" that comes from the netdev notifier; this is because qdev is only
interesting if it was the subject of the state change, _and_ its root
qdisc belongs in the taprio list).

The 'found' variable also doesn't really serve too much of a purpose
either; we can just call taprio_set_picos_per_byte() within the loop,
and exit immediately afterwards.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://lore.kernel.org/r/20220923145921.3038904-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>