[SCSI] fusion core changes for SAS support

 - various bits for SAS support from the LSI driver.
 - use the device private data for the fusion target private data.
   this should be using the midlayer target data framework, but we
   can't move over to that until fusion has been switched to the
   generic DV code
 - use target ID and channel from the fusion target private data,
   because those in scsi_device will be different for mptsas

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>