Move the SCSI status field to private data. Stop setting the .ptr,
.this_residual, .buffer and .buffer_residual SCSI pointer members
since no code in this driver reads these members.

This patch prepares for removal of the SCSI pointer from struct scsi_cmnd.

Link: https://lore.kernel.org/r/20220218195117.25689-38-bvanassche@acm.orgReviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Masanori Goto <gotom@debian.or.jp>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>