USB: fix transvibrator disconnect race

in disconnect you set the interface's private data to NULL. In your IO
methods you unconditionally follow the pointer into never never land.

Signed-off-by: Oliver Neukum <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/trancevibrator.c

···
 	struct trancevibrator *dev;
 
 	dev = usb_get_intfdata (interface);
-	usb_set_intfdata(interface, NULL);
 	device_remove_file(&interface->dev, &dev_attr_speed);
+	usb_set_intfdata(interface, NULL);
 	usb_put_dev(dev->udev);
 	kfree(dev);
 }