QTI devfreq cooling devices.

The devfreq cooling device will be used by userspace thermal daemon to
vote for frequency cap under thermal conditions. This driver will register a
cooling device for the GPU phandle specified in the devicetree.

Properties:
- compatible:
	Usage: required
	Value type: <string>
	Definition: should be "qcom,devfreq-cdev"

Cooling device node:
- qcom,devfreq:
	Usage: required
	Value type: <devfreq phandle>
	Definition: Phandle to the GPU devfreq. This will register the GPU
			devfreq as a cooling device with thermal framework.

Example:
	qcom,devfreq-cdev {
		compatible = "qcom,devfreq-cdev";
		qcom,devfreq = <&msm_gpu>;
        };