ALSA: line6: Use correct endpoint type for midi output

Sending MIDI messages to a PODxt through the USB connection shows
"usb_submit_urb failed" in dmesg and the message is not received by
the POD.

The error is caused because in the funcion send_midi_async() in midi.c
there is a call to usb_sndbulkpipe() for endpoint 3 OUT, but the PODxt
USB descriptor shows that this endpoint it's an interrupt endpoint.

Patch tested with PODxt only.

[ The bug has been present from the very beginning in the staging
  driver time, but Fixes below points to the commit moving to sound/
  directory so that the fix can be cleanly applied -- tiwai ]

Fixes: 61864d84 ("ALSA: move line6 usb driver into sound/usb")
Signed-off-by: Fabián Inostroza <fabianinostroza@udec.cl>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/line6/midi.c

@@ -125,7 +125,7 @@ static int send_midi_async(struct usb_line6 *line6, unsigned char *data,
 	}
 
 	usb_fill_int_urb(urb, line6->usbdev,
-			 usb_sndbulkpipe(line6->usbdev,
+			 usb_sndintpipe(line6->usbdev,
 					 line6->properties->ep_ctrl_w),
 			 transfer_buffer, length, midi_sent, line6,
 			 line6->interval);