drm/amd/powerplay: add deep sleep initialization

This patch adds the deep sleep initialization at DPM, it needs send a
message to SMC to enable this feature before enable voltage controller.

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