Documentation: arm: 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"

		"qcom,msm8996-l2cc"

- reg:		This specifies the base address and size of

		the register region.

Optional properties:

- reg:		An optional second tuple specifies the shared common base

		address required to trigger the L2 SPM out of power collapse.

- qcom,vctl-node: Reference to a node that controls the power rails for the

 cluster.

- qcom,vctl-val: The voltage control register value that must be set before

		the caches can be turned on. This would be a required property

		if the target necessitates a voltage rail be turned on before

		turning on the cache.

Example:

	clock-controller@f900f000 {

		compatible = "qcom,8994-l2ccc"";

		reg = <0xf900f000 0x1000>,

			<0xf911210c 0x4>;

		qcom,vctl-node = <&cluster_node>;

		qcom,vctl-val = <0xb8>;

	}