arm64: dts: rockchip: Add vdd_cpu_big reg to rk3588-edgeble-ncm6

The RK8602 and RK8603 voltage regulators on the Rock 5B board provide
the power lines vdd_cpu_big0 and vdd_cpu_big1, respectively.

Add the necessary device tree nodes and bind them to the corresponding
CPU big core nodes.

Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Link: https://lore.kernel.org/r/20231125190522.87607-6-jagan@edgeble.ai


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