Binding for TI fixed factor rate clock sources.

This binding uses the common clock binding[1], and also uses the autoidle
support from TI autoidle clock [2].

[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
[2] Documentation/devicetree/bindings/clock/ti/autoidle.txt

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

Optional properties:
- clock-output-names : from common clock binding.
- ti,autoidle-shift: bit shift of the autoidle enable bit for the clock,
  see [2]
- reg: offset for the autoidle register of this clock, see [2]
- ti,invert-autoidle-bit: autoidle is enabled by setting the bit to 0, see [2]
- ti,set-rate-parent: clk_set_rate is propagated to parent

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

	dpll_usb_clkdcoldo_ck: dpll_usb_clkdcoldo_ck {
		#clock-cells = <0>;
		compatible = "ti,fixed-factor-clock";
		clocks = <&dpll_usb_ck>;
		ti,clock-div = <1>;
		ti,autoidle-shift = <8>;
		reg = <0x01b4>;
		ti,clock-mult = <1>;
		ti,invert-autoidle-bit;
	};