ARM: bcm2835: Add Raspberry Pi's ACT LED to DT

The Raspberry Pi board has one GPIO-controlled LED labeled "ACT". Add it
to the DT via the gpio-leds driver, so users can control it from
userspace. If CONFIG_LEDS_TRIGGER_HEARTBEAT is set, the LED will also
signal some sign of life.

The GPIO circuitry is low-active. And as the bootloader may decide to
switch the LED on at boot time, the default state is 'keep'.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

arch/arm/boot/dts/bcm2835-rpi-b.dts

@@ -8,6 +8,17 @@
 	memory {
 		reg = <0 0x10000000>;
 	};
+
+	leds {
+		compatible = "gpio-leds";
+
+		act {
+			label = "ACT";
+			gpios = <&gpio 16 1>;
+			default-state = "keep";
+			linux,default-trigger = "heartbeat";
+		};
+	};
 };
 
 &gpio {