Binding for Qualcomm Atheros AR7xxx/AR9XXX PLL controller

The PPL controller provides the 3 main clocks of the SoC: CPU, DDR and AHB.

Required Properties:
- compatible: has to be "qca,<soctype>-cpu-intc" and one of the following
  fallbacks:
  - "qca,ar7100-pll"
  - "qca,ar7240-pll"
  - "qca,ar9130-pll"
  - "qca,ar9330-pll"
  - "qca,ar9340-pll"
  - "qca,qca9550-pll"
- reg: Base address and size of the controllers memory area
- clock-names: Name of the input clock, has to be "ref"
- clocks: phandle of the external reference clock
- #clock-cells: has to be one

Optional properties:
- clock-output-names: should be "cpu", "ddr", "ahb"

Example:

	memory-controller@18050000 {
		compatible = "qca,ar9132-ppl", "qca,ar9130-pll";
		reg = <0x18050000 0x20>;

		clock-names = "ref";
		clocks = <&extosc>;

		#clock-cells = <1>;
		clock-output-names = "cpu", "ddr", "ahb";
	};