drm/amd/powerplay: correct vega12 bootup values settings

The vbios firmware structure changed between v3_1 and v3_2. So,
the code to setup bootup values needs different paths based
on header version.

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