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>
2 files changed