spi: spi-rockchip: Add rk3588-spi compatible

This adds a compatible string for the SPI controller found in
the RK3588 and RK3588s SoCs.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220830124452.33561-1-sebastian.reichel@collabora.com


Signed-off-by: Mark Brown <broonie@kernel.org>