Bindings for Linear Technologies LT3593 LED controller

Required properties:
- compatible:		Should be "lltc,lt3593".
- lltc,ctrl-gpios:	A handle to the GPIO that is connected to the 'CTRL'
			pin of the chip.

The hardware supports only one LED. The properties of this LED are
configured in a sub-node in the device node.

Optional sub-node properties:
- function:		See Documentation/devicetree/bindings/leds/common.txt
- color:		See Documentation/devicetree/bindings/leds/common.txt
- label:		A label for the LED. If none is given, the LED will be
			named "lt3595::" (deprecated)
- linux,default-trigger: The default trigger for the LED.
			See Documentation/devicetree/bindings/leds/common.txt
- default-state:	The initial state of the LED.
			See Documentation/devicetree/bindings/leds/common.txt

If multiple chips of this type are found in a design, each one needs to
be handled by its own device node.

Example:

#include <dt-bindings/leds/common.h>

led-controller {
	compatible = "lltc,lt3593";
	lltc,ctrl-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>;

	led {
		function = LED_FUNCTION_BACKLIGHT;
		color = <LED_COLOR_ID_WHITE>;
		default-state = "on";
	};
};
