drm/sched: Cancel and flush all outstanding jobs before finish.

To avoid any possible use after free.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/414814/
CC: stable@vger.kernel.org
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/scheduler/sched_main.c

@@ -899,6 +899,9 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
 	if (sched->thread)
 		kthread_stop(sched->thread);
 
+	/* Confirm no work left behind accessing device structures */
+	cancel_delayed_work_sync(&sched->work_tdr);
+
 	sched->ready = false;
 }
 EXPORT_SYMBOL(drm_sched_fini);