PinePhone uses PWM backlight and a XBD599 LCD panel over DSI for
display.

Backlight levels curve was optimized by Martijn Braam using a
lux meter.

Add its device nodes.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Martijn Braam <martijn@brixit.nl>
Signed-off-by: Ondrej Jirman <megous@megous.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200702081432.1727696-2-megous@megous.comSigned-off-by: Maxime Ripard <maxime@cerno.tech>