Commit a9994687 ("vfio/display: core & wireup") added display
support to vfio-pci with the default being "auto", which breaks
existing VMs when the vGPU requires GL support but had no previous
requirement for a GL compatible configuration.  "Off" is the safer
default as we impose no new requirements to VM configurations.

Fixes: a9994687 ("vfio/display: core & wireup")
Cc: qemu-stable@nongnu.org
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>