Merge remote-tracking branch 'remotes/afaerber/tags/qom-devices-for-peter' into staging

QOM infrastructure fixes and device conversions

* Fixes for -device foo,help

# gpg: Signature made Tue 04 Nov 2014 17:27:41 GMT using RSA key ID 3E7E013F
# gpg: Good signature from "Andreas Färber <afaerber@suse.de>"
# gpg:                 aka "Andreas Färber <afaerber@suse.com>"

* remotes/afaerber/tags/qom-devices-for-peter:
  qdev: Use qdev_get_device_class() for -device <type>,help
  qdev: Move error printing to the end of qdev_device_help()
  qdev: Create qdev_get_device_class() function

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