arm64: dts: rockchip: support poweroff on the rock-5b

Allow the rock-5b to poweroff its pmic. When issuing a "shutdown -h now"
on the rock-5b it reboots instead. Defining 'system-power-controller'
allows the rk806 to power down.

Commit c699fbfd ("arm64: dts: rockchip: Support poweroff on
NanoPC-T6") similarly resolves this issue for the nanopc-t6.
Signed-off-by: John Clark <inindev@gmail.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20231225222859.17153-1-inindev@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts

@@ -426,6 +426,8 @@ pmic@0 {
 		pinctrl-0 = <&pmic_pins>, <&rk806_dvs1_null>,
 			    <&rk806_dvs2_null>, <&rk806_dvs3_null>;
 
+		system-power-controller;
+
 		vcc1-supply = <&vcc5v0_sys>;
 		vcc2-supply = <&vcc5v0_sys>;
 		vcc3-supply = <&vcc5v0_sys>;