dt-bindings: add documentation for msm-bus proxy client

Bus Proxy Client Bindings

Bus proxy client provides means to cast proxy bandwidth votes during bootup

which is removed at the end of boot. This feature can be used in situations

where a shared resource can be scaled between several possible perfomance

levels and hardware requires that it be at a high level at the beginning of

boot before the client has probed and voted for required bandwidth.

Required properties:

- compatible:			Must be "qcom,bus-proxy-client".

Optional properties:

- qcom,msm-bus,name:		String representing the client-name.

- qcom,msm-bus,num-cases:	Total number of usecases.

- qcom,msm-bus,active-only:	Boolean context flag for requests in active or

				dual (active & sleep) contex.

- qcom,msm-bus,num-paths:	Total number of master-slave pairs.

- qcom,msm-bus,vectors-KBps:	Arrays of unsigned integers representing:

				master-id, slave-id, arbitrated bandwidth

				in KBps, instantaneous bandwidth in KBps.

Example:

	qcom,proxy-client {

		compatible = "qcom,bus-proxy-client";

		qcom,msm-bus,name = "proxy_client";

		qcom,msm-bus,num-cases = <3>;

		qcom,msm-bus,num-paths = <2>;

		qcom,msm-bus,active-only;

		qcom,msm-bus,vectors-KBps =

			<22 512 0 0>, <23 512 0 0>,

			<22 512 0 6400000>, <23 512 0 6400000>,

			<22 512 0 6400000>, <23 512 0 6400000>;

	};