RPMh regulator cooling device.

The RPMh regulator cooling device, will be used to place a voltage floor
restriction on a rail. This cooling device will use a QMP AOP mail box to send
the message to apply and clear voltage floor restriction.

The cooling device node should be a child of the regulator devicetree node,
which it is trying to place the floor restriction.

Properties:

- compatible:
	Usage: required
	Value type: <string>
	Definition: shall be "qcom,rpmh-reg-cdev"

- qcom,reg-resource-name:
	Usage: required
	Value type: <string>
	Definition: The regulator resource name to be used for communicating
			with RPMh. This value should be any of the below
			resource name,
			cx -> For CX rail,
			mx -> For MX rail,
			ebi -> For EBI rail.

- mboxes:
	Usage: required
	Value type: <phandle>
	Definition: A phandle to the QMP AOP mail box, that needs to be used
			for sending the floor restriction message.

- #cooling-cells: Must be 2. Please refer to
			<devicetree/bindings/thermal/thermal.txt> for more
			details.

Example:

	vdd_cx: rpmh-cx-regulator-cdev {
		compatible = "qcom,rpmh-reg-cdev";
		mboxes = <&qmp_aop 0>;
		qcom,reg-resource-name = "cx";
		#cooling-cells = <2>;
	};