drm/amd/pm: add one new function to get 32 bit feature mask for vangogh

This patch is to add one new function to get 32 bit feature mask for
vangogh.

Signed-off-by: Xiaojian Du <Xiaojian.Du@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>