These are never freed in the nominal path.  A domain_device has a
different lifetime than a sas_rphy we need a dev->rphy independent way
of identifying sata devices.
Reviewed-by: NJack Wang <jack_wang@usish.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>