drm/amd/powerplay: limit smu support to Arcturus for onevf

Under onevf mode the smu support to other chips is not well
verified yet.

Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>