drm/amd/powerplay: move od_default_setting callback to asic file

the set default od_setting is asic related function,
so move thic code to vega20_ppt file.

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