[SCSI] scsi_transport_sas: mapping the rphy channel equal to the port identifier

We will be mapping the RAID volumes in mptsas to a reserved
channel that
is one larger than the anticapated number of ports on the direct
attached host
adapter.

Signed-off-by: Eric Moore <Eric.Moore@lsil.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>