drm/amd/display: Revert "drm/amd/display: Add a check for idle power optimization"

Revert commit 434cf7af

 ("drm/amd/display: Add a check for idle power optimization")
Because it cause Freesync and S4 regression

Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Sung Joon Kim <sungkim@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>