ovl: rename ovl_cleanup_unlocked() to ovl_cleanup()

ovl: rename ovl_cleanup_unlocked() to ovl_cleanup()

The only remaining user of ovl_cleanup() is ovl_cleanup_locked(), so we
no longer need both.

This patch renames ovl_cleanup() to ovl_cleanup_locked() and makes it
static.
ovl_cleanup_unlocked() is renamed to ovl_cleanup().

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250716004725.1206467-22-neil@brown.name
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>