drm/amd/powerplay: correct Arcturus OD support

OD is not supported on Arcturus. Thus the
pp_od_clk_voltage sysfs interface is also not supported.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>