scsi_debug: re-order file scope declarations

Group most defines together first; followed by struct definitions and
then table and variable definitions. Normalize all function headers.

[mkp: Corrected hex value in WP/DPOFUA MODE SENSE comment]
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>