disp: msm: add inverted display brightness value property

In general the brightness value, the first parameter is low byte and
the second is high byte, but some DDIC invert, so add inverted display
brightness value property.

Change-Id: Ic635eb745709d756f093738348e471a544a2eeb1
Signed-off-by: Althaf Neelanchirayil <aneelanc@codeaurora.org>