arm64: dts: rockchip: Add Lunzn Fastrhino R68S

It's similar to Fastrhino R66S with the following changes:
+ 2/4GB LPDDR4 RAM
+ 2x 1000 Base-T (native, RTL8211f)
+ ADC button
+ 16GB eMMC on-board
- No SD card slot

Signed-off-by: Tianling Shen <cnsztl@gmail.com>
Link: https://lore.kernel.org/r/20230506061108.17658-3-cnsztl@gmail.com


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