backlight: add support for Sharp SL-6000 LCD and backlight drivers

On Sharp SL-6000 lcd/backlight is a bit complex, so add two drivers
one for lcd-driving chip, other one for dac regulating the backlight
LEDS.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
5 files changed