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/mdt.c b/fs/nilfs2/mdt.c
index 6790ca6..800e8d7 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -66,7 +66,7 @@
 	kunmap_atomic(kaddr, KM_USER0);
 
 	set_buffer_uptodate(bh);
-	nilfs_mark_buffer_dirty(bh);
+	mark_buffer_dirty(bh);
 	nilfs_mdt_mark_dirty(inode);
 	return 0;
 }
@@ -355,7 +355,7 @@
 	err = nilfs_mdt_read_block(inode, block, 0, &bh);
 	if (unlikely(err))
 		return err;
-	nilfs_mark_buffer_dirty(bh);
+	mark_buffer_dirty(bh);
 	nilfs_mdt_mark_dirty(inode);
 	brelse(bh);
 	return 0;