arm64: dts: rockchip: fix poweroff on helios64

Adding the rockchip,system-power-controller property here will use the
rk808 to power off the system.

Fixes: 09e006cf ("arm64: dts: rockchip: Add basic support for Kobol's Helios64")
Signed-off-by: Florian Klink <flokli@flokli.de>
Tested-by: Dennis Gilmore <dgilmore@redhat.com>
Link: https://lore.kernel.org/r/20211020095926.735938-2-flokli@flokli.deSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-kobol-helios64.dts

@@ -276,6 +276,7 @@ rk808: pmic@1b {
 		clock-output-names = "xin32k", "rk808-clkout2";
 		pinctrl-names = "default";
 		pinctrl-0 = <&pmic_int_l>;
+		rockchip,system-power-controller;
 		vcc1-supply = <&vcc5v0_sys>;
 		vcc2-supply = <&vcc5v0_sys>;
 		vcc3-supply = <&vcc5v0_sys>;