f2fs: avoid to flush nat journal entries

This patch adds a missing condition which flushes nat journal entries
unnecessarily introduced by:

    f2fs: add bitmaps for empty or full NAT blocks
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -2513,7 +2513,7 @@ void flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	 * entries, remove all entries from journal and merge them
 	 * into nat entry set.
 	 */
-	if (cpc->reason == CP_UMOUNT ||
+	if (enabled_nat_bits(sbi, cpc) ||
 		!__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
 		remove_nats_in_journal(sbi);