Btrfs: cleanup for btrfs_btree_balance_dirty

- 'nr' is no more used.
- btrfs_btree_balance_dirty() and __btrfs_btree_balance_dirty() can share
  a bunch of code.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 2025a91..305c33e 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -62,8 +62,8 @@
 struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
 					      struct btrfs_key *location);
 int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info);
-void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr);
-void __btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr);
+void btrfs_btree_balance_dirty(struct btrfs_root *root);
+void btrfs_btree_balance_dirty_nodelay(struct btrfs_root *root);
 void btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root);
 void btrfs_mark_buffer_dirty(struct extent_buffer *buf);
 int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,