Binding for simple fixed factor rate clock sources.

This binding uses the common clock binding[1].

[1] Documentation/devicetree/bindings/clock/clock-bindings.txt

Required properties:
- compatible : shall be "fixed-factor-clock".
- #clock-cells : from common clock binding; shall be set to 0.
- clock-div: fixed divider.
- clock-mult: fixed multiplier.
- clocks: parent clock.

Optional properties:
- clock-output-names : From common clock binding.

Some clocks that require special treatments are also handled by that
driver, with the compatibles:
  - allwinner,sun4i-a10-pll3-2x-clk

Example:
	clock {
		compatible = "fixed-factor-clock";
		clocks = <&parentclk>;
		#clock-cells = <0>;
		clock-div = <2>;
		clock-mult = <1>;
	};