scsi: scsi_trace: Use get_unaligned_be24()

scsi: scsi_trace: Use get_unaligned_be24()

This makes the SCSI tracing code slightly easier to read.

Link: https://lore.kernel.org/r/20200313203102.16613-6-bvanassche@acm.org
Fixes: bf8162354233 ("[SCSI] add scsi trace core functions and put trace points")
Cc: Christoph Hellwig <hch@lst.de>
Cc: James E.J. Bottomley <jejb@linux.ibm.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Reported-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>