mfd: Add ROHM BD9571MWV-M PMIC DT bindings

Add DT bindings for the ROHM BD9571MWV-M PMIC. This PMIC has
the following features:
- multiple voltage monitors for 1V8, 2V5, 3V3 voltage rail
- one voltage regulator for DVFS
- two GPIOs

Signed-off-by: Marek Vasut <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/mfd/bd9571mwv.txt

···
+* ROHM BD9571MWV Power Management Integrated Circuit (PMIC) bindings
+
+Required properties:
+ - compatible		: Should be "rohm,bd9571mwv".
+ - reg			: I2C slave address.
+ - interrupt-parent	: Phandle to the parent interrupt controller.
+ - interrupts		: The interrupt line the device is connected to.
+ - interrupt-controller	: Marks the device node as an interrupt controller.
+ - #interrupt-cells	: The number of cells to describe an IRQ, should be 2.
+			    The first cell is the IRQ number.
+			    The second cell is the flags, encoded as trigger
+			    masks from ../interrupt-controller/interrupts.txt.
+ - gpio-controller      : Marks the device node as a GPIO Controller.
+ - #gpio-cells          : Should be two.  The first cell is the pin number and
+                            the second cell is used to specify flags.
+                            See ../gpio/gpio.txt for more information.
+ - regulators:          : List of child nodes that specify the regulator
+                            initialization data. Child nodes must be named
+                            after their hardware counterparts:
+			     - vd09
+			     - vd18
+			     - vd25
+			     - vd33
+			     - dvfs
+			    Each child node is defined using the standard
+			    binding for regulators.
+
+Example:
+
+	pmic: pmic@30 {
+		compatible = "rohm,bd9571mwv";
+		reg = <0x30>;
+		interrupt-parent = <&gpio2>;
+		interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		gpio-controller;
+		#gpio-cells = <2>;
+
+		regulators {
+			dvfs: dvfs {
+				regulator-name = "dvfs";
+				regulator-min-microvolt = <750000>;
+				regulator-max-microvolt = <1030000>;
+				regulator-boot-on;
+				regulator-always-on;
+			};
+		};
+	};