vfio: add license tag to some files

Add SPDX-License-Identifier to some files missing it in hw/vfio/.

Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250623093053.1495509-1-john.levon@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
4 files changed