ALSA: usb-audio: 6fire: return correct XRUN indication

Return SNDRV_PCM_POS_XRUN (snd_pcm_uframes_t) instead of
SNDRV_PCM_STATE_XRUN (snd_pcm_state_t) from the pointer
function of 6fire, as expected by snd_pcm_update_hw_ptr0().

Caught by sparse.
Signed-off-by: NEldad Zack <eldad@fogrefinery.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/6fire/pcm.c

@@ -543,7 +543,7 @@ static snd_pcm_uframes_t usb6fire_pcm_pointer(
 	snd_pcm_uframes_t ret;
 
 	if (rt->panic || !sub)
-		return SNDRV_PCM_STATE_XRUN;
+		return SNDRV_PCM_POS_XRUN;
 
 	spin_lock_irqsave(&sub->lock, flags);
 	ret = sub->dma_off;