libvirt xen: Add just device_video
libvirt xen: Add just device_video

Re-introduce part of "libvirt xen: Add gfx_passthru and device_video"
commit by Artur Puzio <contact@puzio.waw.pl>

QubesOS/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin