ARM: at91/dt: sama5d4 xplained: enable the led D8

Enable D8 led as now the pioD is available. D8 is the power led and is on by
default.
Signed-off-by: Josh Wu <josh.wu@atmel.com>
[nicolas.ferre@atmel.com: split the patch in 2]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91-sama5d4_xplained.dts

@@ -246,7 +246,7 @@ leds {
 		d8 {
 			label = "d8";
 			gpios = <&pioD 30 GPIO_ACTIVE_HIGH>;
-			status = "disabled";
+			default-state = "on";
 		};
 
 		d10 {