drm/amd/powerplay: use existed smu_dpm_set* interfaces to implement powergate functions

Abstract powergate_vcn/jpeg functions, using smu_dpm_set* to implement it.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>