vdsm: move video device to vmdevices

No code changes, only moving around

Change-Id: I40ba700e6223490251af86189196f189ae4bad39
Signed-off-by: Martin Polednik <mpolednik@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29263
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>