arm64: dts: rockchip: use pin constants to describe gpios

Use macros to describe gpios will make the dts easier to
read and write.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
[converted interrupt-gpios and new rk3399-evb backlight]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>