GFX-Display: fix CABC control interface not work

GFX-Display: fix CABC control interface not work

BZ: 35376

1. CABC disable and enable control is missing, when
some one add code to control CABC backlight reduce range
according backligh level.

2. if control interface not work, the CABC will be always
on , then we can not measure the power reduce.

Change-Id: I5e7e33b0f8fe2656e63afb3a14f01f7c2ea8969d
Signed-off-by: Ke Ai <ke.ai@intel.com>
Reviewed-on: http://android.intel.com:8080/49122
Reviewed-by: Xu, Randy <randy.xu@intel.com>
Reviewed-by: Geng, Xiujun <xiujun.geng@intel.com>
Tested-by: Tong, BoX <box.tong@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>