mdpy is a sample pci device for vfio-mdev.  Not (yet) merged upstream,
patch available here:

https://www.kraxel.org/cgit/linux/commit/?h=vfio-sample-display&id=6fd86cff3d7df38ab89625b16fdd6434b1c18749



Cc: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>