Qualcomm Technologies, Inc's USB Gadget

Required properties:
- compatible: Should be "qcom,usb-gadget".
- qcom,composition: List of configurations where each is separated by '|'.
	And each configuration has comma separated list of functions
	specified as: <f1_name>.<f1_instance_name>,<f2_name>....
- qcom,vid: VendorId to be used by composite device.
- qcom,pid: ProductId to be used by composite device.

Optional properties:
- qcom,class: Class of composite device.
- qcom,subclass: SubClass of composite device.
- qcom,protocol: Protocol of composite device.

Examples:
	usb_gadget {
		compatible = "qcom,usb-gadget";
		qcom,composition = "rndis.rndis|ecm.ecm";
		qcom,vid = <0x05c6>;
		qcom,pid = <0x9057>;
	};
