drm/amdgpu: use a timer for fence fallback

Less overhead than a work item and also adds proper cleanup handling.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 615ce6d..3630cb5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -389,7 +389,6 @@
  * Fences.
  */
 struct amdgpu_fence_driver {
-	struct amdgpu_ring		*ring;
 	uint64_t			gpu_addr;
 	volatile uint32_t		*cpu_addr;
 	/* sync_seq is protected by ring emission lock */
@@ -398,7 +397,7 @@
 	bool				initialized;
 	struct amdgpu_irq_src		*irq_src;
 	unsigned			irq_type;
-	struct delayed_work             lockup_work;
+	struct timer_list		fallback_timer;
 	wait_queue_head_t		fence_queue;
 };