ALSA: usb-audio: add implicit fb quirk for Behringer UFX1204

Add quirk to ensure a sync endpoint is properly configured.
This patch is a fix for same symptoms on Behringer UFX1204 as patch
from Albertto Aquirre on Dec 8 2016 for Axe-Fx II.

Signed-off-by: Lassi Ylikojola <lassi.ylikojola@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/pcm.c

@@ -352,6 +352,15 @@ static int set_sync_ep_implicit_fb_quirk(struct snd_usb_substream *subs,
 		ep = 0x86;
 		iface = usb_ifnum_to_if(dev, 2);
 
+		if (!iface || iface->num_altsetting == 0)
+			return -EINVAL;
+
+		alts = &iface->altsetting[1];
+		goto add_sync_ep;
+	case USB_ID(0x1397, 0x0002):
+		ep = 0x81;
+		iface = usb_ifnum_to_if(dev, 1);
+
 		if (!iface || iface->num_altsetting == 0)
 			return -EINVAL;