CABC(Content Adaptive Backlight Control) is used to
increase the contrast of such LCD-screens the backlight
can be (globally) dimmed when the image to be displayed
is dark (i.e. not comprising high intensity image data)
while the image data is numerically corrected and adapted
to the reduced backlight intensity.
Change-Id: I0bd84375264675943f1b601f0cac8b843567087d
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>