[legal] Add some missing FILE_LICENCE declarations

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

src/hci/commands/digest_cmd.c

  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>

src/hci/commands/gdbstub_cmd.c

  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdio.h>
 #include <errno.h>
 #include <assert.h>

src/hci/commands/time_cmd.c

  * Shao Miller <shao.miller@yrdsb.edu.on.ca>.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>