[SCSI] scsi_transport_sas: kill the use of channel

Using the port_id for the channel is completely unnecessary since the
host_id/target_id are constructed to be globally unique.  Also move
the mptsas driver on to virtual channel 1 for its raid devices.

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