f2fs: fix a potential out of range issue

Fix a potential out of range issue introduced by commit:
22fb72225a
f2fs: simplify write_orphan_inodes for better readable
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/checkpoint.c

@@ -323,9 +323,9 @@ static void write_orphan_inodes(struct f2fs_sb_info *sbi, block_t start_blk)
 			memset(orphan_blk, 0, sizeof(*orphan_blk));
 		}
 
-		orphan_blk->ino[nentries] = cpu_to_le32(orphan->ino);
+		orphan_blk->ino[nentries++] = cpu_to_le32(orphan->ino);
 
-		if (nentries++ == F2FS_ORPHANS_PER_BLOCK) {
+		if (nentries == F2FS_ORPHANS_PER_BLOCK) {
 			/*
 			 * an orphan block is full of 1020 entries,
 			 * then we need to flush current orphan blocks