drm/amd/display: arbitration find the matching dig-az first.

[Description]
this change is in branch already.
without this change, after resume, az_inst might swapped.

Signed-off-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>