drm/amd/display: Re-arrange GFX9 fields

For more clear usage in future

Signed-off-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>