ALSA: line6: Make common PCM pointer callback

Both playback and capture callbacks are identical, so let's merge
them.

Tested-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/line6/pcm.c

@@ -266,6 +266,15 @@ int snd_line6_trigger(struct snd_pcm_substream *substream, int cmd)
 	return 0;
 }
 
+/* common PCM pointer callback */
+snd_pcm_uframes_t snd_line6_pointer(struct snd_pcm_substream *substream)
+{
+	struct snd_line6_pcm *line6pcm = snd_pcm_substream_chip(substream);
+	struct line6_pcm_stream *pstr = get_stream(line6pcm, substream->stream);
+
+	return pstr->pos_done;
+}
+
 /* Acquire and start duplex streams:
  * type is either LINE6_STREAM_IMPULSE or LINE6_STREAM_MONITOR
  */