net_sched: remove impossible conditions

We no longer allow "handle" to be zero, so there is no need to check
for that.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/Ywd4NIoS4aiilnMv@kili


Signed-off-by: Jakub Kicinski <kuba@kernel.org>