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>

fs/overlayfs/util.c

@@ -978,7 +978,7 @@ int ovl_set_protattr(struct inode *inode, struct dentry *upper,
 	return 0;
 }
 
-/**
+/*
  * Caller must hold a reference to inode to prevent it from being freed while
  * it is marked inuse.
  */