drm/amd/pm: check specific index for aldebaran

Check for specific indexes that may be invalid values.

Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>