btrfs: roll tracepoint into btrfs_space_info_update helper

We duplicate this tracepoint everywhere we call these helpers, so update
the helper to have the tracepoint as well.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>