DFLL PMIC integration node in the board DTS file

Required properties:
- pmic-i2c-interface : selects the I2C interface to communicate with
                       the PMIC.  Future driver changes should add
                       support for the PWM interface, at which point
                       this should no longer be mandatory
- pmic-i2c-address : cell containing the PMIC I2C address
- pmic-i2c-voltage-register : cell containing the I2C register address of the
                              PMIC's set-output-voltage register, for the
                              rail that supplies the DFLL
- i2c-fs-rate : cell containing the I2C bus rate in Hz, in FS mode
- dfll-min-microvolt : minimum voltage in microvolts that the DFLL will
                       attempt to program the PMIC to supply
- dfll-max-microvolt : maximum voltage in microvolts that the DFLL will
                       attempt to program the PMIC to supply

Optional properties:
- i2c-10-bit-addresses : PMIC requires a 10-bit I2C address
- i2c-hs-rate : use high-speed I2C to communicate with the PMIC, at this
                rate (in Hz)
- i2c-hs-master-code : I2C master code to use - only applies in HS mode;
                       i2c-hs-rate must be set

Example:

cpu_dfll_pmic_integration {
        pmic-i2c-interface;
        pmic-i2c-address = <0x86>;
        pmic-i2c-voltage-register = <0x00>;
        i2c-fs-rate = <400000>;
        dfll-min-microvolt = <600000>;
        dfll-max-microvolt = <1400000>;
};