dt-bindings: serial: snps-dw-apb-uart: Add Rockchip RK3588

Add a Rockchip RK3588 compatible.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20220623161350.242079-1-sebastian.reichel@collabora.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>