There is no user of this function anymore.

This was forgotten to be removed in commit a575ceeb
("Btrfs: get rid of unused orphan infrastructure").
Signed-off-by: NMisono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>