drm/panthor: fix for dma-fence safe access rules

drm/panthor: fix for dma-fence safe access rules

Commit 506aa8b02a8d6 ("dma-fence: Add safe access helpers and document
the rules") details the dma-fence safe access rules. The most common
culprit is that drm_sched_fence_get_timeline_name may race with
group_free_queue.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Cc: stable@vger.kernel.org # v6.17+
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251204174545.399059-1-olvaffe@gmail.com