ARM: dts: microchip: gardena-smart-gateway: Fix power LED

When starting up, the GARDENA smart Gateway's power LED should be
flashing green. It is unclear why this has not been done earlier.

The LED frequency cannot be configured in the devicetree. Luckily, the
default is 1 Hz, which is what we want.

Signed-off-by: Ezra Buehler <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Claudiu Beznea <[e-mail]>

arch/arm/boot/dts/microchip/at91sam9g25-gardena-smart-gateway.dts

···
 		led-power-green {
 			label = "smartgw:power:green";
 			gpios = <&pioC 20 GPIO_ACTIVE_HIGH>;
-			default-state = "on";
+			linux,default-trigger = "timer";
 		};
 
 		led-power-red {