Analog Devices ADF5355/ADF4355 device driver

Required properties:
	- compatible: Should be one of
		* "adi,adf5355": When using the ADF5355 device
		* "adi,adf5356": When using the ADF5356 device
		* "adi,adf4355": When using the ADF4355 device
		* "adi,adf4355-2": When using the ADF4355-2 device
		* "adi,adf4355-3": When using the ADF4355-3 device
	- reg: SPI chip select numbert for the device
	- spi-max-frequency: Max SPI frequency to use (< 20000000)
	- clocks: From common clock binding. Clock is phandle to clock for
		ADF5355 Reference Clock (CLKIN).

Optional properties:
	- gpios:	GPIO Lock detect - If set with a valid phandle and GPIO
			number, pll lock state is tested upon read.
	- clock-output-names : From common clock binding to override the
			default output clock name.
	- adi,power-up-frequency: If set in Hz the PLL tunes to
			the desired frequency on probe.
	- adi,reference-div-factor: If set the driver skips dynamic calculation
			and uses this default value instead.
	- adi,reference-doubler-enable: Enables reference doubler.
	- adi,reference-div2-enable: Enables reference divider.
	- adi,reference-differential-input-enable: The device permits use of
			either differential or single ended reference sources.
			For differential sources set this property.
	- adi,phase-detector-polarity-negative-enable: When a passive loop
			filter or a noninverting active loop filter is used,
			clear for positive. If an active filter with an
			inverting characteristic is used, set this to negative.
	- adi,charge-pump-current: Set the charge pump current in uA.
			Set this value to the charge pump current that the loop
			filter is designed with. For the lowest spurs, the
			900 uA setting is recommended.
	- adi,charge-pump-negative-bleed-enable: Use of constant negative bleed.
			(recommended for most fractional-N applications)
	- adi,charge-pump-gated-bleed-enable: Enables gated bleed.
	- adi,charge-pump-bleed-current-polarity-enable: Sets the polarity of
			the charge pump bleed current.
	- adi,muxout-select: On chip multiplexer output selection.
			Valid values for the multiplexer output are:
			0: Three-State Output (default)
			1: DVDD
			2: DGND
			3: R-Counter output
			4: N-Divider output
			5: Analog lock detect
			6: Digital lock detect
	- adi,muxout-level-3v3-enable: MUXOUT is programmable to two logic
			levels. Clear this to select 1.8 V logic,
			and set it to select 3.3 V logic.
	- adi,mute-till-lock-enable: If enabled, the supply current to the RF
			output stage is shut down until the device achieves lock,
			as determined by the digital lock detect circuitry.
	- adi,output-b-enable: Enables or disables the primary RF output
	- adi,output-a-enable: Enables or disables the auxiliary/high RF output
	- adi,output-a-power: Primary RF output power selection.
			Valid values for the power mode are:
			0: -4dBm (default)
			1: -1dBm
			2: +2dBm
			3: +5dBm
	- adi,output-b-power: Auxiliary output power selection.
			Valid values for the power mode are:
			0: -4dBm (default)
			1: -1dBm
			2: +2dBm
			3: +5dBm


Example:
			adf5355@0 {
				compatible = "adf5355";
				reg = <0>;
				spi-max-frequency = <1000000>;
				clocks = <&adf4351_clkin>;
				clock-names = "clkin";
				clock-output-names = "adf5355_out";
				adi,charge-pump-current = <900>;
				adi,muxout-select = <6>;
				adi,mute-till-lock-enable;
				adi,output-a-power = <2>;
				adi,output-b-power = <2>;
				adi,output-b-enable;
				adi,output-a-enable;
				adi,charge-pump-negative-bleed-enable;
				adi,reference-differential-input-enable;
				adi,muxout-level-3v3-enable;
				adi,power-up-frequency = <123000000>;
			};
