drm/amd/display: prepare dml 2.1 for new asic

[Why&How]
prepare dml 2.1 for new asic

Acked-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Dmytro Laktyushkin <dmytro.laktyushkin@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>