Hisilicon Hi655x Voltage regulators

Note:
The hi655x regulator control is managed by hi655x Power IC.
So the node of this regulator must be child node of hi655x
pmic node.

The driver uses the regulator core framework, so please also
take the bindings of regulator.txt for reference.

Required properties:
- compatible: Must be "hisilicon,hi655x-regulator-pmic";
- regulator-ctrl-regs: Registers offset of control register,
  In turn with enable disable and status register offset.
- regulator-ctrl-mask: The control mask bit of the register.
- regulator-vset-regs: Voltage set register offset.
- regulator-vset-mask: voltage set control mask.
- regulator-n-vol: The num of support voltages.
- regulator-vset-table: The table of support voltages.

Example:
        pmic: pmic@f8000000 {
                compatible = "hisilicon,hi655x-pmic";
		...
		ldo7: regulator@a26 {
			compatible = "hisilicon,hi655x-regulator-pmic";
			regulator-name = "ldo7";
			regulator-min-microvolt = <1800000>;
			regulator-max-microvolt = <3300000>;
			regulator-valid-modes-mask = <0x0a>;
			regulator-enable-ramp-delay = <120>;
			regulator-ctrl-regs = <0x029 0x02a 0x02b>;
			regulator-ctrl-mask = <0x6>;
			regulator-vset-regs = <0x078>;
			regulator-vset-mask = <0x7>;
			regulator-n-vol = <8>;
			regulator-vset-table  = <1800000>,<1850000>,
						<2850000>,<2900000>,
						<3000000>,<3100000>,
						<3200000>,<3300000>;
		};
		...
	}
