ALSA: usb-audio: Enable S/PDIF on the ASUS Xonar U3

The only required change is to extend the existing Xonar U1
mixer quirks to the U3, which seems to be controlled the same
way.
Signed-off-by: Denis Washington <denisw@online.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer_quirks.c

@@ -430,6 +430,8 @@ static void snd_audigy2nx_proc_read(struct snd_info_entry *entry,
 	}
 }
 
+/* ASUS Xonar U1 / U3 controls */
+
 static int snd_xonar_u1_switch_get(struct snd_kcontrol *kcontrol,
 				   struct snd_ctl_elem_value *ucontrol)
 {
@@ -1305,8 +1307,9 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
 		err = snd_ftu_create_mixer(mixer);
 		break;
 
-	case USB_ID(0x0b05, 0x1739):
-	case USB_ID(0x0b05, 0x1743):
+	case USB_ID(0x0b05, 0x1739): /* ASUS Xonar U1 */
+	case USB_ID(0x0b05, 0x1743): /* ASUS Xonar U1 (2) */
+	case USB_ID(0x0b05, 0x17a0): /* ASUS Xonar U3 */
 		err = snd_xonar_u1_controls_create(mixer);
 		break;