msm: mdss: add eDP backlight

Add configuration for setting different brightness levels in edp driver.
This is done according to lpg channel and period values from devicetree.

Change-Id: I4e9074d777102193d7678f7aac565be3a5a551df
Signed-off-by: Asaf Penso <apenso@codeaurora.org>
5 files changed