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/gcinode.c b/fs/nilfs2/gcinode.c
index 6e79ac0..08a07a2 100644
--- a/fs/nilfs2/gcinode.c
+++ b/fs/nilfs2/gcinode.c
@@ -157,15 +157,11 @@
 	if (buffer_dirty(bh))
 		return -EEXIST;
 
-	if (buffer_nilfs_node(bh)) {
-		if (nilfs_btree_broken_node_block(bh)) {
-			clear_buffer_uptodate(bh);
-			return -EIO;
-		}
-		nilfs_btnode_mark_dirty(bh);
-	} else {
-		nilfs_mark_buffer_dirty(bh);
+	if (buffer_nilfs_node(bh) && nilfs_btree_broken_node_block(bh)) {
+		clear_buffer_uptodate(bh);
+		return -EIO;
 	}
+	mark_buffer_dirty(bh);
 	return 0;
 }