arm64: dts: rockchip: add ADC buttons to rk3588-evb1

The Rockchip EVB1 has a couple of buttons connected via an ADC
line. Let's add them to its devicetree.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20231005134357.37171-1-sebastian.reichel@collabora.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>