drm/amdgpu/powerplay: fix AVFS handling with custom powerplay table

When a custom powerplay table is provided, we need to update
the OD VDDC flag to avoid AVFS being enabled when it shouldn't be.

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=205393
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>