[legal] Add missing FILE_LICENCE declarations

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

src/include/sys/time.h

  * Date and time
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdint.h>
 
 /** Seconds since the Epoch

src/include/time.h

  * Date and time
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <sys/time.h>
 #include <ipxe/time.h>