ufs: Convert directory handling to kmap_local

Remove kmap use and use folio_release_kmap() instead of ufs_put_page().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>