Merge remote-tracking branch 'remotes/kraxel/tags/audio-20191018-pull-request' into staging

audio: bugfixes, pa connection and stream naming.
audio: 5.1/7.1 support for alsa, pa and usb-audio.

# gpg: Signature made Fri 18 Oct 2019 08:41:26 BST
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/audio-20191018-pull-request:
  paaudio: fix channel order for usb-audio 5.1 and 7.1 streams
  usbaudio: change playback counters to 64 bit
  usb-audio: support more than two channels of audio
  usb-audio: do not count on avail bytes actually available
  audio: basic support for multichannel audio
  audio: replace shift in audio_pcm_info with bytes_per_frame
  audio: support more than two channels in volume setting
  paaudio: get/put_buffer functions
  audio: make mixeng optional
  audio: add mixing-engine option (documentation)
  audio: paaudio: ability to specify stream name
  audio: paaudio: fix connection and stream name
  audio: fix parameter dereference before NULL check

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>