arm: kirkwood: openblocks-a6: add support for Init button

The Kirkwood-based PlatHome OpenBlocks A6 board has an Init button
connected to MPP pin 38. This commit adds support for this button.
Signed-off-by: NThomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: NAndrew Lunn <andrew@lunn.ch>
Tested-by: NAtsushi Yamagata <yamagata@plathome.co.jp>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/kirkwood-openblocks_a6.dts

@@ -151,4 +151,18 @@
 			gpios = <&gpio1 11 1>;
 		};
         };
+
+	gpio_keys {
+		compatible = "gpio-keys";
+		pinctrl-0 = <&pmx_gpio_init>;
+		pinctrl-names = "default";
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		button@1 {
+			label = "Init Button";
+			linux,code = <116>;
+			gpios = <&gpio1 6 0>;
+		};
+	};
 };