Binding for TI CDCE913/925/937/949 programmable I2C clock synthesizers.

Reference
This binding uses the common clock binding[1].

[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
[2] https://www.ti.com/product/cdce913
[3] https://www.ti.com/product/cdce925
[4] https://www.ti.com/product/cdce937
[5] https://www.ti.com/product/cdce949

The driver provides clock sources for each output Y1 through Y5.

Required properties:
 - compatible: Shall be one of the following:
	- "ti,cdce913": 1-PLL, 3 Outputs
	- "ti,cdce925": 2-PLL, 5 Outputs
	- "ti,cdce937": 3-PLL, 7 Outputs
	- "ti,cdce949": 4-PLL, 9 Outputs
 - reg: I2C device address.
 - clocks: Points to a fixed parent clock that provides the input frequency.
 - #clock-cells: From common clock bindings: Shall be 1.

Optional properties:
 - xtal-load-pf: Crystal load-capacitor value to fine-tune performance on a
                 board, or to compensate for external influences.

For all PLL1, PLL2, ... an optional child node can be used to specify spread
spectrum clocking parameters for a board.
  - spread-spectrum: SSC mode as defined in the data sheet.
  - spread-spectrum-center: Use "centered" mode instead of "max" mode. When
    present, the clock runs at the requested frequency on average. Otherwise
    the requested frequency is the maximum value of the SCC range.


Example:

	clockgen: cdce925pw@64 {
		compatible = "cdce925";
		reg = <0x64>;
		clocks = <&xtal_27Mhz>;
		#clock-cells = <1>;
		xtal-load-pf = <5>;
		/* PLL options to get SSC 1% centered */
		PLL2 {
			spread-spectrum = <4>;
			spread-spectrum-center;
		};
	};
