Set scsi_host_template.cmd_size instead of using the SCSI pointer for
storing driver-private data. Change the type of the argument of
uas_add_work() from struct uas_cmd_info * into struct scsi_cmnd * because
it is easier to convert a SCSI command pointer into a uas_cmd_info pointer
than the other way around.

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

Link: https://lore.kernel.org/r/20220218195117.25689-46-bvanassche@acm.org
Cc: linux-usb@vger.kernel.org
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>