Binding for Fairchild FAN53555 regulators

Required properties:
  - compatible: one of "fcs,fan53555", "silergy,syr827", "silergy,syr828"
  - reg: I2C address

Optional properties:
  - fcs,suspend-voltage-selector: declare which of the two available
		voltage selector registers should be used for the suspend
		voltage. The other one is used for the runtime voltage setting
		Possible values are either <0> or <1>
  - vin-supply: regulator supplying the vin pin

Example:

	regulator@40 {
		compatible = "fcs,fan53555";
		regulator-name = "fan53555";
		regulator-min-microvolt = <1000000>;
		regulator-max-microvolt = <1800000>;
		vin-supply = <&parent_reg>;
		fcs,suspend-voltage-selector = <1>;
	};
