QTI DDR cooling device.

The DDR cooling device will be used to place a DDR frequency vote. This
cooling device will be used in those cases where all the subsystem's are
thermally throttled and DDR has to be operated with a minimum performance
level. This cooling device vote can ensure the same.

Properties:
- compatible:
	Usage: required
	Value type: <string>
	Definition: should be "qcom,ddr-cooling-device".

Bus Scaling Data:
- qcom,msm-bus,name:
	Usage: required
	Value type: <string>
	Definition: String describing DDR cooling device client. It is defined
		at Documentation/devicetree/bindings/arm/msm/msm_bus.txt.
- qcom,msm-bus,num-cases:
	Usage: required
	Value type: <integer>
	Definition: This is the number of Bus Scaling use cases
		defined in the vectors property. This must be set to more than
		one for DDR cooling device based on different levels of DDR
		frequency cooling support required. The use-case0 always should
		be a vote to take off DDR cdev votes from the system. It is
		defined at Documentation/devicetree/bindings/arm/msm/msm_bus.txt.
- qcom,msm-bus,active-only:
	Usage: optional
	Value type: <None>
	Definition: A boolean flag indicating if it is active only
		bandwidth vote. It is defined at
		Documentation/devicetree/bindings/arm/msm/msm_bus.txt.
- qcom,msm-bus,num-paths:
	Usage: required
	Value type: <integer>
	Definition: This represents total number of master-slave pairs for
		different usecases. It is defined at
		Documentation/devicetree/bindings/arm/msm/msm_bus.txt.
- qcom,msm-bus,vectors-KBps:
	Usage: required
	Value type: <array>
	Definition: A series of 4 cell properties, with a format of
		(src, dst, ab, ib). It is defined at
		Documentation/devicetree/bindings/arm/msm/msm_bus.txt.

Cooling Device Property:
- #cooling-cells:
	Usage: required
	Value type: <integer>
	Definition: Must be 2. Needed for of_thermal as cooling device
			identifier. Please refer to
			<devicetree/bindings/thermal/thermal.txt> for more
			details.
Example:
	qcom,ddr-cdev {
		compatible = "qcom,ddr-cooling-device";
		qcom,msm-bus,name = "ddr-cdev";
		qcom,msm-bus,num-cases = <2>;
		qcom,msm-bus,num-paths = <1>;
		qcom,msm-bus,vectors-KBps = <1 512 0 0>,
					<1 512 0 366000>;
		#cooling-cells = <2>;
        };