drm/amdgpu: asd function needs to be unloaded in suspend phase

Unload ASD function in suspend phase.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>