ARM: dts: rockchip: change to "max-frequency" from "clock-freq-min-max" on rv1108

"clock-freq-min-max" was deprecated. There is only using in rv1108.dtsi.
Use the "max-frequency" for removiing "clock-freq-min-max" in future.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>