viocd: add dummy audio ioctl handler

Make sure audio_ioctl is always defined even if being a dummy function
since the cdrom_ioctl interface assumes its existence and we don't
want to BUG on null ptr on some ioctls like, e.g. CDROMREADTOCENTRY,
CDROMREADTOCHDR etc. when we fix CDC_PLAY_AUDIO checking in cdrom.c.

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/cdrom/viocd.c

@@ -550,12 +550,19 @@ return_complete:
 	}
 }
 
+static int viocd_audio_ioctl(struct cdrom_device_info *cdi, unsigned int cmd,
+			     void *arg)
+{
+	return -EINVAL;
+}
+
 static struct cdrom_device_ops viocd_dops = {
 	.open = viocd_open,
 	.release = viocd_release,
 	.media_changed = viocd_media_changed,
 	.lock_door = viocd_lock_door,
 	.generic_packet = viocd_packet,
+	.audio_ioctl = viocd_audio_ioctl,
 	.capability = CDC_CLOSE_TRAY | CDC_OPEN_TRAY | CDC_LOCK | CDC_SELECT_SPEED | CDC_SELECT_DISC | CDC_MULTI_SESSION | CDC_MCN | CDC_MEDIA_CHANGED | CDC_PLAY_AUDIO | CDC_RESET | CDC_DRIVE_STATUS | CDC_GENERIC_PACKET | CDC_CD_R | CDC_CD_RW | CDC_DVD | CDC_DVD_R | CDC_DVD_RAM | CDC_RAM
 };