Fix the race at reconnection of the device.
The disconnected usb_chip[] must be cleared before the next probe
call properly.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
 
 static int snd_usb_audio_free(struct snd_usb_audio *chip)
 {
-       usb_chip[chip->index] = NULL;
        kfree(chip);
        return 0;
 }
                list_for_each(p, &chip->mixer_list) {
                        snd_usb_mixer_disconnect(p);
                }
+               usb_chip[chip->index] = NULL;
                mutex_unlock(®ister_mutex);
                snd_card_free_when_closed(card);
        } else {