qxl: add sanity check

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Merge remote-tracking branch 'remotes/spice/tags/pull-spice-3' into staging

qxl: add sanity check

# gpg: Signature made Mon 24 Feb 2014 12:01:27 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/spice/tags/pull-spice-3:
  qxl: add sanity check

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