regulator: add devicetree bindings for Fairchild FAN53555 regulators

Document the regulator and add a fairchild vendor-prefix.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/fan53555.txt

+Binding for Fairchild FAN53555 regulators
+
+Required properties:
+  - compatible: "fcs,fan53555"
+  - 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>;
+	};

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -49,6 +49,7 @@ epson	Seiko Epson Corp.
 est	ESTeem Wireless Modems
 eukrea  Eukréa Electromatique
 excito	Excito
+fcs	Fairchild Semiconductor
 fsl	Freescale Semiconductor
 GEFanuc	GE Fanuc Intelligent Platforms Embedded Systems, Inc.
 gef	GE Fanuc Intelligent Platforms Embedded Systems, Inc.