drm/panfrost: Fix scheduler workqueue bug

When the GPU scheduler was ported to using a struct for its
initialization parameters, it was overlooked that panfrost creates a
distinct workqueue for timeout handling.

The pointer to this new workqueue is not initialized to the struct,
resulting in NULL being passed to the scheduler, which then uses the
system_wq for timeout handling.

Set the correct workqueue to the init args struct.

Cc: stable@vger.kernel.org # 6.15+
Fixes: 796a9f55 ("drm/sched: Use struct for drm_sched_init() params")
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Closes: https://lore.kernel.org/dri-devel/b5d0921c-7cbf-4d55-aa47-c35cd7861c02@igalia.com/


Signed-off-by: Philipp Stanner <phasta@kernel.org>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20250709102957.100849-2-phasta@kernel.org