ARM: shmobile: armadillo: dts: Add gpio-keys device

The board had 4 buttons connected to GPIOs, add a corresponding
gpio-keys device.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7740-armadillo800eva-reference.dts

@@ -72,6 +72,35 @@ reg_5p0v: regulator@3 {
 		regulator-boot-on;
 	};
 
+	gpio-keys {
+		compatible = "gpio-keys";
+
+		power-key {
+			gpios = <&pfc 99 GPIO_ACTIVE_LOW>;
+			linux,code = <116>;
+			label = "SW3";
+			gpio-key,wakeup;
+		};
+
+		back-key {
+			gpios = <&pfc 100 GPIO_ACTIVE_LOW>;
+			linux,code = <158>;
+			label = "SW4";
+		};
+
+		menu-key {
+			gpios = <&pfc 97 GPIO_ACTIVE_LOW>;
+			linux,code = <139>;
+			label = "SW5";
+		};
+
+		home-key {
+			gpios = <&pfc 98 GPIO_ACTIVE_LOW>;
+			linux,code = <102>;
+			label = "SW6";
+		};
+	};
+
 	leds {
 		compatible = "gpio-leds";
 		led1 {