mvebu: puzzle-m902: add GPIO reset button

Add reset button to device tree so it has the function expected from
usual OpenWrt devices.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

target/linux/mvebu/files/arch/arm64/boot/dts/marvell/cn9132-puzzle-m902.dts

@@ -8,6 +8,7 @@
 #include "cn9130.dtsi"
 
 #include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
 
 / {
 	model = "iEi Puzzle-M902";
@@ -49,6 +50,16 @@
 		reg = <0x0 0x0 0x0 0x80000000>;
 	};
 
+	gpio_keys {
+		compatible = "gpio-keys";
+
+		reset {
+			label = "Reset";
+			linux,code = <KEY_RESTART>;
+			gpios = <&cp0_gpio2 4 GPIO_ACTIVE_LOW>;
+		};
+	};
+
 	cp2_reg_usb3_vbus0: cp2_usb3_vbus@0 {
 		compatible = "regulator-fixed";
 		regulator-name = "cp2-xhci0-vbus";