drm/amdgpu: when suspending, if uvd/vce was running. need to cancel delay work.

fix the issue that when resume back, uvd/vce
dpm was disabled and uvd/vce's performace
dropped.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org