Binding for Maxim MAX77686 32k clock generator block

This is a part of device tree bindings of MAX77686 multi-function device.
More information can be found in bindings/mfd/max77686.txt file.

The MAX77686 contains three 32.768khz clock outputs that can be controlled
(gated/ungated) over I2C.

Following properties should be presend in main device node of the MFD chip.

Required properties:
- #clock-cells: simple one-cell clock specifier format is used, where the
  only cell is used as an index of the clock inside the provider. Following
  indices are allowed:
    - 0: 32khz_ap clock,
    - 1: 32khz_cp clock,
    - 2: 32khz_pmic clock.

Example: Node of the MFD chip

	max77686: max77686@09 {
		compatible = "maxim,max77686";
		interrupt-parent = <&wakeup_eint>;
		interrupts = <26 0>;
		reg = <0x09>;
		#clock-cells = <1>;

		/* ... */
	};

Example: Clock consumer node

	foo@0 {
		compatible = "bar,foo";
		/* ... */
		clock-names = "my-clock";
		clocks = <&max77686 2>;
	};