Nanopi R6: show boot progress on the system LED

Set up openwrt to show boot progress on the nanopi R6S or R6C system LED.

The LED blinking states indicate the boot stage. The led is defined as
a power LED, but can still be set to heartbeat in /etc/config/system
after the system is done booting.

--- a/arch/arm64/boot/dts/rockchip/rk3588s-nanopi-r6.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3588s-nanopi-r6.dtsi
@@ -16,6 +16,10 @@
 		ethernet0 = &gmac1;
 		mmc0 = &sdmmc;
 		mmc1 = &sdhci;
+		led-boot = &sys_led;
+		led-failsafe = &sys_led;
+		led-running = &sys_led;
+		led-upgrade = &sys_led;
 	};
 
 	chosen {
@@ -54,9 +58,9 @@
 
 		sys_led: led-0 {
 			color = <LED_COLOR_ID_RED>;
-			function = LED_FUNCTION_HEARTBEAT;
+			function = LED_FUNCTION_POWER;
 			gpios = <&gpio1 RK_PC1 GPIO_ACTIVE_HIGH>;
-			linux,default-trigger = "heartbeat";
+			default-state = "on";
 			pinctrl-names = "default";
 			pinctrl-0 = <&sys_led_pin>;
 		};