[legal] Relicense files under GPL2_OR_LATER_OR_UBDL

Relicense files with kind permission from

    Stefan Hajnoczi <stefanha@redhat.com>

alongside the contributors who have already granted such relicensing
permission.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/virtio-net.c

@@ -20,7 +20,7 @@
  * See the COPYING file in the top-level directory.
  */
 
-FILE_LICENCE ( GPL2_OR_LATER );
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <errno.h>
 #include <stdlib.h>

src/drivers/net/vxge/vxge.c

@@ -5,7 +5,7 @@
  * as "vxge" even though the code is in vxge_* named files.
  */
 
-FILE_LICENCE(GPL2_OR_LATER);
+FILE_LICENCE(GPL2_OR_LATER_OR_UBDL);
 
 #include <ipxe/pci.h>