drm/amd/display: enable dcn35 idle power optimization

[Why]
Idle power optimization was disabled on dcn35 by default.

[How]
Enable by setting disable_idle_power_optimizations to false.

Signed-off-by: Roman Li <roman.li@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>