ARM: dts: ixp4xx: Add beeper to the NSLU2

This adds the beeper GPIO to the NSLU2 completing the board
support.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/intel-ixp42x-linksys-nslu2.dts

@@ -90,6 +90,11 @@ gpio-poweroff {
 		timeout-ms = <5000>;
 	};
 
+	gpio-beeper {
+		compatible = "gpio-beeper";
+		gpios = <&gpio0 4 GPIO_ACTIVE_HIGH>;
+	};
+
 	soc {
 		bus@50000000 {
 			/* The first 16MB region at CS0 on the expansion bus */