ARM: dts: rockchip: Add LEDs via gpio-leds for Radxa Rock2 Square

Describe the two user-controllable LEDs on Rock2 Square boards.
All information have been retrieved from the schematics and the vendor
devicetree. The default-triggers mimic the behaviour of the vendor-kernel to
keep functionalities in sync.
Signed-off-by: NRomain Perier <romain.perier@gmail.com>
Reviewed-by: NSjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288-rock2-square.dts

@@ -49,6 +49,22 @@
 		stdout-path = "serial2:115200n8";
 	};
 
+	gpio-leds {
+		compatible = "gpio-leds";
+
+		heartbeat {
+			gpios = <&gpio7 15 GPIO_ACTIVE_LOW>;
+			label = "rock2:green:state1";
+			linux,default-trigger = "heartbeat";
+		};
+
+		mmc {
+			gpios = <&gpio0 11 GPIO_ACTIVE_LOW>;
+			label = "rock2:blue:state2";
+			linux,default-trigger = "mmc0";
+		};
+	};
+
 	ir: ir-receiver {
 		compatible = "gpio-ir-receiver";
 		gpios = <&gpio8 1 GPIO_ACTIVE_LOW>;