drm/amd/powerplay: implement is_support_sw_smu function for new smu

add this helper to check new sw-smu support.

Signed-off-by: Kevin Wang <Kevin1.Wang@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>