USB: rtl8150_disconnect() needs tasklet_kill()

We need to wait until any currently-running handler has completed. Fixes an
unplug-time oops reported by "Miles Lane" <[e-mail]>.

Cc: "Petko Manolov" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/net/rtl8150.c

···
 	if (dev) {
 		set_bit(RTL8150_UNPLUG, &dev->flags);
 		tasklet_disable(&dev->tl);
+		tasklet_kill(&dev->tl);
 		unregister_netdev(dev->netdev);
 		unlink_all_urbs(dev);
 		free_all_urbs(dev);