f2fs: remove redundant set_page_dirty from write_compacted_summaries

Previously, set_page_dirty is called every time after writting one summary info
into compacted summary page,
To avoid redundant set_page_dirty, we only call set_page_dirty before release
page.

Signed-off-by: Yu Chao <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>