Documentation: msm: Introduce L2 cache clock controller bindings

L2 Cache Clock Controller

The L2 Cache Clock Controller provides clock, power domain, and

reset control to a L2-cache for a cluster. There is L2CCC register

region per CPU Cluster.

Required properties:

- compatible:	Can be one of:

		"qcom,8994-l2ccc"

		"qcom,8916-l2ccc"

- reg:		This specifies the base address and size of

		the register region.

Example:

	clock-controller@f900f000 {

		compatible = "qcom,8994-l2ccc"";

		reg = <0xf900f000 0x1000>;

	}