dt-bindings: thermal: Add snapshot of devfreq-vdd-cdev

Qualcomm Technologies, Inc. Devfreq Vdd cooling device

The Devfreq Vdd cooling device, will be used to set minimum

operating level for gfx rail using gpu devfreq interface

during cold thermal condition. This cooling device will be

used with cold temp monitor thermal zone. Whenever cold

temperature triggers, it disables frequencies lower than

the minimum operating level using devfreq opp API's.

Required Parameters:

- compatible:

	Usage: required

	Value type: <string>

	Definition: should be "qcom,devfreq-vdd-cooling-device"

- 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.

- #cooling-cells:

	Usage: required

	Value type: <integer>

	Definition: Must be 2. This is required by of-thermal and refer the doc

		<devicetree/bindings/thermal/thermal.txt> for more details.

Example:

	devfreq_vdd_cdev: devfreq-vdd-cdev {

		compatible = "qcom,devfreq-vdd-cooling-device";

		devfreq = <&msm_gpu>;

		#cooling-cells = <2>;

	};