drm/amdgpu/mes: fix use-after-free issue

Delete fence fallback timer to fix the ramdom
use-after-free issue.

v2: move to amdgpu_mes.c
Signed-off-by: Jack Xiao <Jack.Xiao@amd.com>
Acked-by: Lijo Lazar <lijo.lazar@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c

@@ -1132,6 +1132,7 @@ void amdgpu_mes_remove_ring(struct amdgpu_device *adev,
 		return;
 
 	amdgpu_mes_remove_hw_queue(adev, ring->hw_queue_id);
+	del_timer_sync(&ring->fence_drv.fallback_timer);
 	amdgpu_ring_fini(ring);
 	kfree(ring);
 }