usb_gadget_unregister_driver — unregister a gadget driver
int usb_gadget_unregister_driver (struct usb_gadget_driver * driver);
Call this in your gadget driver's module cleanup function,
to tell the underlying usb controller that your driver is
going away. If the controller is connected to a USB host,
it will first disconnect. The driver is also requested
to unbind and clean up any device state, before this procedure
finally returns.
This function must be called in a context that can sleep.