Revert "drm/amd/display: Speed up DML fast_validate path"

This reverts commit 1b5d0e7e.

It caused corruption in some media players.

Tested-by: Daniel Wheeler <Daniel.Wheeler@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Reviewed-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Martin Leung <Martin.Leung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>