riscv: dts: Add GPIO reboot method to HiFive Unleashed DTS file

Add the ability to reboot the HiFive Unleashed board via GPIO.
Signed-off-by: Yash Shah <yash.shah@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts

@@ -2,6 +2,7 @@
 /* Copyright (c) 2018-2019 SiFive, Inc */
 
 #include "fu540-c000.dtsi"
+#include <dt-bindings/gpio/gpio.h>
 
 /* Clock frequency (in Hz) of the PCB crystal for rtcclk */
 #define RTCCLK_FREQ		1000000
@@ -41,6 +42,10 @@ rtcclk: rtcclk {
 		clock-frequency = <RTCCLK_FREQ>;
 		clock-output-names = "rtcclk";
 	};
+	gpio-restart {
+		compatible = "gpio-restart";
+		gpios = <&gpio 10 GPIO_ACTIVE_LOW>;
+	};
 };
 
 &uart0 {