drm/amd/display: Remove unused code

We have some old code associated with DML, which we had plans to use,
but at some point, we just moved away from it. This commit removes the
dml_wrapper* files since they are not used anymore.

Reported-by: Magali Lemes <magalilemes00@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>