ARM: ux500: Enable LED heartbeat functionality on Snowbal via DT

This patch configures the user LED on Snowball to double flash
every second or so, whilst it's still alive. This can give key
indications as to what the board is doing in the case of no
console output.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

arch/arm/boot/dts/snowball.dts

@@ -78,6 +78,7 @@ used-led {
 			label = "user_led";
 			gpios = <&gpio4 14 0x4>;
 			default-state = "on";
+			linux,default-trigger = "heartbeat";
 		};
 	};