Behringer UFX1604 playback (snd-usb-audio) pops, clicks.
--------------------------------------------------------

Workaround:

in /linux/sound/usb/pcm.c in line 342:

```
case USB_ID(0x1397, 0x0002): /* Behringer UFX1204 */
        ep = 0x81;
        ifnum = 1;
        goto add_sync_ep_from_ifnum;
```
needs to be:

```
case USB_ID(0x1397, 0x0002): /* Behringer UFX1204 */
case USB_ID(0x1397, 0x0001): /* Behringer UFX1604 */
        ep = 0x81;
        ifnum = 1;
        goto add_sync_ep_from_ifnum;
```
for Behringer UFX1604

Tested with new compiled snd-usb-audio.ko. Playback ok without clicks.

relates to commit: 

https://github.com/torvalds/linux/commit/5e35dc0338d85ccebacf3f77eca1e5dea73155e8#diff-bb3848ab95be1b898fb7f15d8beae70c