scsi: csiostor: Mark known unused variable as __always_unused

scsi: csiostor: Mark known unused variable as __always_unused

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

 drivers/scsi/csiostor/csio_hw.c: In function ‘csio_hw_get_vpd_params’:
 drivers/scsi/csiostor/csio_hw.c:309:8: warning: variable ‘s’ set but not used [-Wunused-but-set-variable]

Link: https://lore.kernel.org/r/20200723122446.1329773-22-lee.jones@linaro.org
Cc: Arkadiusz Drabczyk <arkadiusz@drabczyk.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>