drm/amd/display: DIG mapping change is causing a blocker

[Why]
DIG mapping change is causing a blocker

[How]
Revert the change for now. We will re-implement it later.

Reviewed-by: Jimmy Kizito <jimmy.kizito@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Zhan Liu <Zhan.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>