hda-audio: qom cleanups

Add HDA_AUDIO type and macro, drop DO_UPCAST().

Had to add a abstract hda audio class as parent
for all hda-* variants to make that fly.  Killed
some init code duplication while being at it.

Cc: Andreas Färber <afaerber@suse.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Merge remote-tracking branch 'remotes/kraxel/tags/pull-audio-3' into staging

hda-audio: qom cleanups

# gpg: Signature made Mon 24 Feb 2014 12:19:48 GMT using RSA key ID D3E87138
# 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>"

* remotes/kraxel/tags/pull-audio-3:
  hda-audio: qom cleanups

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