usb: ci_udc: clean up all allocations in unregister

usb_gadget_unregister_driver() is called to tear down the USB device mode
stack. Fix the driver to stop the USB HW (which causes any attached host
to notice the disappearance of the device), and free all allocations
(which obviously prevents memory leaks).

Signed-off-by: Stephen Warren <swarren@nvidia.com>

drivers/usb/gadget/ci_udc.c

@@ -875,5 +875,11 @@ int usb_gadget_register_driver(struct usb_gadget_driver *driver)
 
 int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
 {
+	udc_disconnect();
+
+	ci_ep_free_request(&controller.ep[0].ep, &controller.ep0_req->req);
+	free(controller.items_mem);
+	free(controller.epts);
+
 	return 0;
 }