arm64: dts: rockchip: mark system power controller on rk3588-evb1

Mark the primary PMIC as system-power-controller, so that the
system properly shuts down on poweroff.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20240117191555.86138-1-sebastian.reichel@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>