f2fs: avoid unnecessary folio_clear_uptodate() for cleanup

In error path of __get_node_folio(), if the folio is not uptodate, let's
avoid unnecessary folio_clear_uptodate() for cleanup.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>