drm/panthor: Drop a WARN_ON() in group_free_queue()

drm/panthor: Drop a WARN_ON() in group_free_queue()

It appears the timeout can still be enabled when we reach that point,
because of the asynchronous progress check done on queues that resets
the timer when jobs are still in-flight, but progress was made.
We could add more checks to make sure the timer is not re-enabled when
a group can't run anymore, but we don't have a group to pass to
queue_check_job_completion() in some context.

It's just as safe (we just want to be sure the timer is stopped before
we destroy the queue) and simpler to drop the WARN_ON() in
group_free_queue().

v2:
- Collect R-bs

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20251203121750.404340-2-boris.brezillon@collabora.com