drm/amd/display: Revert "drm/amd/display: disable idle optimizations"

This reverts commit e7ef5569e71bf3fec01ea513c27c6081c0dbbc64.

Idle optimization was disabled due to SMU and firmware bugs. Enable it
back for DCN32. DCN321 has them enabled already

Fixes: 6a640b95 ("drm/amd/display: disable idle optimizations")
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-and-tested-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>