MAX8907 regulator

Required properties:
- compatible: "maxim,max8907"
- reg: I2C slave address
- interrupts: The interrupt output of the controller
- mbatt-supply: The input supply for MBATT, BBAT, SDBY, VRTC.
- in-v1-supply: The input supply for SD1.
- in-v2-supply: The input supply for SD2.
- in-v3-supply: The input supply for SD3.
- in1-supply: The input supply for LDO1.
...
- in20-supply: The input supply for LDO20.
- regulators: A node that houses a sub-node for each regulator within the
  device. Each sub-node is identified using the node's name (or the deprecated
  regulator-compatible property if present), with valid values listed below.
  The content of each sub-node is defined by the standard binding for
  regulators; see regulator.txt.

Optional properties:
- maxim,system-power-controller: Boolean property indicating that the PMIC
  controls the overall system power.

The valid names for regulators are:

  sd1, sd2, sd3, ldo1, ldo2, ldo3, ldo4, ldo5, ldo6, ldo7, ldo8, ldo9, ldo10,
  ldo11, ldo12, ldo13, ldo14, ldo15, ldo16, ldo17, ldo18, ldo19, ldo20, out5v,
  out33v, bbat, sdby, vrtc.

Example:

		max8907@3c {
			compatible = "maxim,max8907";
			reg = <0x3c>;
			interrupts = <0 86 0x4>;

			maxim,system-power-controller;

			mbatt-supply = <&some_reg>;
			in-v1-supply = <&mbatt_reg>;
			...
			in1-supply = <&mbatt_reg>;
			...

			regulators {
				mbatt_reg: mbatt {
					regulator-name = "vbat_pmu";
					regulator-min-microvolt = <5000000>;
					regulator-max-microvolt = <5000000>;
					regulator-always-on;
				};

				sd1 {
					regulator-name = "nvvdd_sv1,vdd_cpu_pmu";
					regulator-min-microvolt = <1000000>;
					regulator-max-microvolt = <1000000>;
					regulator-always-on;
				};

				sd2 {
					regulator-name = "nvvdd_sv2,vdd_core";
					regulator-min-microvolt = <1200000>;
					regulator-max-microvolt = <1200000>;
					regulator-always-on;
				};
...
			};
		};
	};
