Fixes the following W=1 kernel build warning(s):

 drivers/scsi/3w-9xxx.c: In function ‘twa_empty_response_queue’:
 drivers/scsi/3w-9xxx.c:942:24: warning: variable ‘response_que_value’ set but not used [-Wunused-but-set-variable]
 drivers/scsi/3w-9xxx.c: In function ‘twa_scsi_biosparam’:
 drivers/scsi/3w-9xxx.c:1701:23: warning: variable ‘tw_dev’ set but not used [-Wunused-but-set-variable]
 drivers/scsi/3w-9xxx.c: In function ‘twa_scsiop_execute_scsi’:
 drivers/scsi/3w-9xxx.c:1812:22: warning: variable ‘sglist’ set but not used [-Wunused-but-set-variable]

Link: https://lore.kernel.org/r/20210312094738.2207817-30-lee.jones@linaro.org
Cc: Adam Radford <aradford@gmail.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>