Maxim Semiconductor MAX8903 Battery Charger bindings

Required properties:
- compatible: "maxim,max8903" for MAX8903 Battery Charger
- dok-gpios: Valid DC power has been detected (active low, input), optional if uok-gpios is provided
- uok-gpios: Valid USB power has been detected (active low, input), optional if dok-gpios is provided

Optional properties:
- cen-gpios: Charge enable pin (active low, output)
- chg-gpios: Charger status pin (active low, input)
- flt-gpios: Fault pin (active low, output)
- dcm-gpios: Current limit mode setting (DC=1 or USB=0, output)
- usus-gpios: USB suspend pin (active high, output)


Example:

	max8903-charger {
		compatible = "maxim,max8903";
		dok-gpios = <&gpio2 3 GPIO_ACTIVE_LOW>;
		flt-gpios = <&gpio2 2 GPIO_ACTIVE_LOW>;
		chg-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>;
		cen-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
	};
