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

In the Linux kernel, the following vulnerability has been resolved: 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.