arm64: dts: rockchip: Add Powkiddy X55

Add support for the Powkiddy X55. The Powkiddy X55 is a handheld
gaming device with a 720p 5.5 inch screen powered by the Rockchip
RK3566 SoC. It includes a Realtek 8821cs WiFi/BT module, 2 ADC
joysticks powered by 4 dedicated ADC channels, and several GPIO
face buttons. There are 2 SDMMC slots (sdmmc1 and sdmmc3), and an
8GB internal eMMC.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Link: https://lore.kernel.org/r/20231204185719.569021-11-macroalpha82@gmail.com


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