ARM: mvebu: Add DT entry for ReadyNAS Duo v2 to use gpio-poweroff driver

Without that fix, at the end of the shutdown process, the board is
still powered (led glowing, fan running, ...).
Signed-off-by: NArnaud Ebalard <arno@natisbad.org>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/kirkwood-netgear_readynas_duo_v2.dts

 /dts-v1/;
 
+#include <dt-bindings/gpio/gpio.h>
 #include "kirkwood.dtsi"
 #include "kirkwood-6282.dtsi"
 
@@ -60,6 +61,10 @@
 				marvell,pins = "mpp29";
 				marvell,function = "gpio";
 			};
+			pmx_poweroff: pmx-poweroff {
+				marvell,pins = "mpp30";
+				marvell,function = "gpio";
+			};
 		};
 
 		clocks {
@@ -158,6 +163,13 @@
 		};
 	};
 
+	gpio-poweroff {
+		compatible = "gpio-poweroff";
+		pinctrl-0 = <&pmx_poweroff>;
+		pinctrl-names = "default";
+		gpios = <&gpio0 30 GPIO_ACTIVE_LOW>;
+	};
+
         regulators {
                 compatible = "simple-bus";
                 #address-cells = <1>;