dt-bindings: thermal: Add limits CPU voltage cooling device

QTI LMH CPU Voltage cooling devices.

The LMH CPU voltage cooling device will be used to place voltage restriction

vote on CPU railway during cold thermal condition. This cooling device driver

will register one cooling device per LLM, which can be used by thermal zone to

place voltage restriction vote.

Properties:

- compatible:

	Usage: required

	Value type: <string>

	Definition: should be "qcom,lmh-cpu-vdd"

Cooling device node:

- reg:

	Usage: Required

	Value type: <a b>

	Definition: where 'a' is the starting register address of the LLM

			and 'b' is the size of LLM address space.

- #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:

	lmh_cpu_vdd0: qcom,lmh-cpu-vdd@18350800 {

		compatible = "qcom,lmh-cpu-vdd";

		reg =  <0x18350800 0x1000>;

		#cooling-cells = <2>;

	};