ovl: fix misformatted comment

Remove misleading /** prefix from a regular comment.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311121628.byHp8tkv-lkp@intel.com/


Signed-off-by: Amir Goldstein <amir73il@gmail.com>