f2fs: reuse room_for_filename for inline dentry operation

This patch introduces to reuse the existing room_for_filename for inline dentry
operation.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c537699..aa055e3 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1248,6 +1248,7 @@
 struct page *init_inode_metadata(struct inode *, struct inode *,
 							const struct qstr *);
 void update_parent_metadata(struct inode *, struct inode *, unsigned int);
+int room_for_filename(const void *, int, int);
 void f2fs_drop_nlink(struct inode *, struct inode *, struct page *);
 struct f2fs_dir_entry *f2fs_find_entry(struct inode *, struct qstr *,
 							struct page **);