Add devicetree binding for the Radxa ROCK S0 board.

Radxa ROCK S0 is a single-board computer based on the Rockchip RK3308B
SoC in an ultra-compact form factor.
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240521212247.1240226-2-jonas@kwiboo.seSigned-off-by: Heiko Stuebner <heiko@sntech.de>