scsi: initio: Remove unused variable 'prev'

scsi: initio: Remove unused variable 'prev'

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

 drivers/scsi/initio.c: In function ‘initio_find_busy_scb’:
 drivers/scsi/initio.c:869:30: warning: variable ‘prev’ set but not used [-Wunused-but-set-variable]

Link: https://lore.kernel.org/r/20210312094738.2207817-24-lee.jones@linaro.org
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Bas Vermeulen <bvermeul@blackstar.xs4all.nl>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Brian Macy <bmacy@sunshinecomputing.com>
Cc: linux-scsi@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>