[SCSI] libsas: fix sas port naming

Make sas-port naming consistent with the expander-attached case whereby
the phy-id is the last digit in the port name.  Otherwise we get the
random behavior of the allocation order.

Reported-by: Patrick Thomson <patrick.s.thomson@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>