ARM: at91: at91sam9n12: correct pin number of gpio-key

Correct pin number of gpio-key for at91sam9n12ek board.
The pioB4 is connect to LED, the pioB3 use as gpio-key.
Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91sam9n12ek.dts

@@ -137,7 +137,7 @@ gpio_keys {
 
 		enter {
 			label = "Enter";
-			gpios = <&pioB 4 GPIO_ACTIVE_LOW>;
+			gpios = <&pioB 3 GPIO_ACTIVE_LOW>;
 			linux,code = <28>;
 			gpio-key,wakeup;
 		};