TI BQ2560X PMIC battery charger binding

Required properties:
 - compatible: Should be "ti,bq2560x_chg".
 - reg: Address offset of charger register.
 - phys: Contains a phandle to the USB phy.

Optional Properties:
- monitored-battery: phandle of battery characteristics devicetree node.
  The charger uses the following battery properties:
- charge-term-current-microamp: current for charge termination phase.
- constant-charge-voltage-max-microvolt: maximum constant input voltage.
  See Documentation/devicetree/bindings/power/supply/battery.txt
- extcon: used to detect if vbus is high level.
Example:

	bat: battery {
		compatible = "simple-battery";
		charge-term-current-microamp = <120000>;
		constant-charge-voltage-max-microvolt = <4350000>;
		......
	};

	&i2c4 {
		status = "okay";
		clock-frequency = <400000>;

		bq2560x_chg: charger@6a {
			compatible = "ti,bq2560x_chg";
			reg = <0x6a>;
			phys = <&hsphy>;
			monitored-battery = <&bat>;
			extcon = <&extcon_gpio>;
		};
	};
