usb: udc: allow adding and removing the same gadget device

allow usb_del_gadget_udc() and usb add_gadget_udc() to be called
repeatedly on the same gadget->dev structure.

We need to clear the gadget->dev structure so that kobject_init()
doesn't complain about already initialized object.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/core.c

@@ -1273,6 +1273,7 @@ void usb_del_gadget_udc(struct usb_gadget *gadget)
 	flush_work(&gadget->work);
 	device_unregister(&udc->dev);
 	device_unregister(&gadget->dev);
+	memset(&gadget->dev, 0x00, sizeof(gadget->dev));
 }
 EXPORT_SYMBOL_GPL(usb_del_gadget_udc);