Merge remote-tracking branch 'remotes/kraxel/tags/audio-20181029-pull-request' into staging

audio: qom cleanups.

# gpg: Signature made Mon 29 Oct 2018 13:37:09 GMT
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/audio-20181029-pull-request:
  audio: use TYPE_MV88W8618_AUDIO instead of hardcoded string
  audio: use object link instead of qdev property to pass wm8750 reference
  audio: use TYPE_WM8750 instead of a hardcoded string
  hw: AC97: make it more QOMconventional

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