drm/amdgpu: add atpx quirk handling (v2)

drm/amdgpu: add atpx quirk handling (v2)

Add quirks for handling PX/HG systems.  In this case, add
a quirk for a weston dGPU that only seems to properly power
down using ATPX power control rather than HG (_PR3).

v2: append a new weston XT

Signed-off-by: Alex Deucher <[email protected]>
Signed-off-by: Junwei Zhang <[email protected]> (v2)
Reviewed-and-Tested-by: Junwei Zhang <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Acked-by: Christian König <[email protected]>
Cc: [email protected]