drm/amd/display: Disable DCN401 idle optimizations

[WHY&HOW]
Disable to improve stability for now.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Roman Li <roman.li@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>