leds: tlc591xx: Document binding for the TI 8/16 Channel i2c LED driver

Document the binding for the TLC591xx LED driver.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Imre Kaloz <kaloz@openwrt.org>
Cc: Matthew.Fatheree@belkin.com
Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

Documentation/devicetree/bindings/leds/leds-tlc591xx.txt

+LEDs connected to tlc59116 or tlc59108
+
+Required properties
+- compatible: should be "ti,tlc59116" or "ti,tlc59108"
+- #address-cells: must be 1
+- #size-cells: must be 0
+- reg: typically 0x68
+
+Each led is represented as a sub-node of the ti,tlc59116.
+See Documentation/devicetree/bindings/leds/common.txt
+
+LED sub-node properties:
+- reg: number of LED line, 0 to 15 or 0 to 7
+- label: (optional) name of LED
+- linux,default-trigger : (optional)
+
+Examples:
+
+tlc59116@68 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	compatible = "ti,tlc59116";
+	reg = <0x68>;
+
+	wan@0 {
+		label = "wrt1900ac:amber:wan";
+		reg = <0x0>;
+	};
+
+	2g@2 {
+		label = "wrt1900ac:white:2g";
+		reg = <0x2>;
+	};
+
+	alive@9 {
+		label = "wrt1900ac:green:alive";
+		reg = <0x9>;
+		linux,default_trigger = "heartbeat";
+	};
+};