ovl: narrow locking in ovl_rename()

Drop the rename lock immediately after the rename, and use
ovl_cleanup_unlocked() for cleanup.

This makes way for future changes where locks are taken on individual
dentries rather than the whole directory.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250716004725.1206467-10-neil@brown.name


Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>