arm64: dts: rockchip: Drop unchanged max-frequency from rk3588 boards

200MHz is the default rk3588 emmc max-frequency added in dtsi, so why
the board DT files are adding the same value explicitly?

Drop that unchanged property value.

Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20230621064507.479891-1-jagan@edgeble.ai


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