Binding for Texas Instruments APLL clock.

This binding uses the common clock binding[1].  It assumes a
register-mapped APLL with usually two selectable input clocks
(reference clock and bypass clock), with analog phase locked
loop logic for multiplying the input clock to a desired output
clock. This clock also typically supports different operation
modes (locked, low power stop etc.) APLL mostly behaves like
a subtype of a DPLL [2], although a simplified one at that.

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

Required properties:
- compatible : shall be "ti,dra7-apll-clock" or "ti,omap2-apll-clock"
- #clock-cells : from common clock binding; shall be set to 0.
- clocks : link phandles of parent clocks (clk-ref and clk-bypass)
- reg : address and length of the register set for controlling the APLL.
  It contains the information of registers in the following order:
	"control" - contains the control register offset
	"idlest" - contains the idlest register offset
	"autoidle" - contains the autoidle register offset (OMAP2 only)
- ti,clock-frequency : static clock frequency for the clock (OMAP2 only)
- ti,idlest-shift : bit-shift for the idlest field (OMAP2 only)
- ti,bit-shift : bit-shift for enable and autoidle fields (OMAP2 only)

Examples:
	apll_pcie_ck: apll_pcie_ck {
		#clock-cells = <0>;
		clocks = <&apll_pcie_in_clk_mux>, <&dpll_pcie_ref_ck>;
		reg = <0x021c>, <0x0220>;
		compatible = "ti,dra7-apll-clock";
	};

	apll96_ck: apll96_ck {
		#clock-cells = <0>;
		compatible = "ti,omap2-apll-clock";
		clocks = <&sys_ck>;
		ti,bit-shift = <2>;
		ti,idlest-shift = <8>;
		ti,clock-frequency = <96000000>;
		reg = <0x0500>, <0x0530>, <0x0520>;
	};