Merge branch 'topic/usb-audio' into for-linus

* topic/usb-audio:
  ALSA: usb-audio - Fix types taken in min()
  sound: usb-audio: do not make URBs longer than sync packet interval
  sound: usb-audio: add MIDI drain callback
  sound: usb-audio: use multiple output URBs
  sound: usb-audio: use multiple input URBs
  sound: usb-audio: Xonar U1 digital output support