scsi: sym53c8xx: remove some redundant variables

Variables scriptb0 and dp_sgmin are being assigned but are never used
hence they are redundant and can be removed.

Cleans up clang warnings:
warning: variable 'scriptb0' set but not used [-Wunused-but-set-variable]
warning: variable 'dp_sgmin' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>