nilfs2: use mark_buffer_dirty to mark btnode or meta data dirty

This replaces nilfs_mdt_mark_buffer_dirty and nilfs_btnode_mark_dirty
macros with mark_buffer_dirty and gets rid of nilfs_mark_buffer_dirty,
an own mark buffer dirty function.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 34ded2c..587f184 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -901,7 +901,7 @@
 		return err;
 	}
 	nilfs_update_inode(inode, ibh);
-	nilfs_mdt_mark_buffer_dirty(ibh);
+	mark_buffer_dirty(ibh);
 	nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
 	brelse(ibh);
 	return 0;