drm/amd/display: Remove references to unused dml arch version

Clean-up the code to remove references of all unused
dml architecture versions since only dml2 is actively
used.

Reviewed-by: Jun Lei <jun.lei@amd.com>
Acked-by: Hersen Wu <hersenxs.wu@amd.com>
Signed-off-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>