arm64: dts: rockchip: Enable regulators for Radxa E20C

Enable pwm and fixed regulators for Radxa E20C. The pwm regulator is
used to power the CPU and GPU. Note that the LPDDR4 voltage is 1.1V.

Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Link: https://lore.kernel.org/r/20250401120020.976343-3-amadeus@jmu.edu.cn


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