btrfs: take an fs_info directly when the root is not used otherwise

There are loads of functions in btrfs that accept a root parameter
but only use it to obtain an fs_info pointer.  Let's convert those to
just accept an fs_info pointer directly.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index 99c879d..416ae8e 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -129,7 +129,7 @@ int btrfs_qgroup_trace_extent(struct btrfs_trans_handle *trans,
  * Return <0 for error(ENOMEM)
  */
 int btrfs_qgroup_trace_leaf_items(struct btrfs_trans_handle *trans,
-				  struct btrfs_root *root,
+				  struct btrfs_fs_info *fs_info,
 				  struct extent_buffer *eb);
 /*
  * Inform qgroup to trace a whole subtree, including all its child tree