arm64: dts: rockchip: Add LED nodes on rk3399-roc-pc

rk3399-roc-pc has three gpio LEDs, enable them.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Link: https://lore.kernel.org/r/7d8d85c9-5fde-7943-a6b6-639bca38bdc1@fivetechno.de


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