scsi: atp870u: Use standard definitions

Use standard definitions for SCSI commands and return status instead of the
hardcoded values.

Link: https://lore.kernel.org/r/20210113090500.129644-25-hare@suse.de


Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>