arm64: dts: rockchip: Add rk3528 CPU frequency scaling support

arm64: dts: rockchip: Add rk3528 CPU frequency scaling support

By default, the CPUs on RK3528 operates at 1.5GHz. Add CPU frequency and
voltage mapping to the device tree to enable dynamic scaling via cpufreq.

The OPP values come from downstream kernel[1], using a voltage close to
the actual frequency. Frequencies below 1.2GHz have been removed due to
the same voltage.

[1] https://github.com/rockchip-linux/kernel/blob/develop-5.10/arch/arm64/boot/dts/rockchip/rk3528.dtsi

Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://lore.kernel.org/r/20250801080025.558935-2-amadeus@jmu.edu.cn
Signed-off-by: Heiko Stuebner <heiko@sntech.de>