dt-bindings: arm: rockchip: add initial rk3588 boards

Add DT binding documentation for the Rockchip RK3588 EVB1,
Radxa Rock 5 Model A and B.

Co-Developed-by: Christopher Obbard <chris.obbard@collabora.com>
Signed-off-by: Christopher Obbard <chris.obbard@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20230109155801.51642-5-sebastian.reichel@collabora.com


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