usb: gadget: udc: dummy: do not call usb_gadget_unregister_driver()

that call is completely unnecessary because
usb_del_gadget_udc() already makes sure the
gadget driver is properly unregistered from
the UDC.
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/gadget/udc/dummy_hcd.c

@@ -2362,7 +2362,6 @@ static void dummy_stop(struct usb_hcd *hcd)
 
 	dum = hcd_to_dummy_hcd(hcd)->dum;
 	device_remove_file(dummy_dev(hcd_to_dummy_hcd(hcd)), &dev_attr_urbs);
-	usb_gadget_unregister_driver(dum->driver);
 	dev_info(dummy_dev(hcd_to_dummy_hcd(hcd)), "stopped\n");
 }