Since QEMU 2.12, QEMU understands a new vfio-pci device option 'display'
which can be used to turn on display capabilities on vgpu-enabled
mediated devices, IOW emulated GPU devices like QXL will no longer be
needed with vgpu-enable mdevs.
QEMU defaults to 'auto' for the 'display' attribute, which is not
foolproof, so we need to play it safe here and default to display='off'
if this attribute wasn't provided in the XML explicitly.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NErik Skultety <eskultet@redhat.com>