scsi: isci: Remove set but not used 'index'

This addresses the following gcc warning with "make W=1":

drivers/scsi/isci/host.c: In function ‘sci_controller_complete_io’:
drivers/scsi/isci/host.c:2674:6: warning: variable ‘index’ set but not
used [-Wunused-but-set-variable]
 2674 |  u16 index;
      |      ^~~~~

Link: https://lore.kernel.org/r/20200827125851.428071-1-yanaijie@huawei.comReported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/isci/host.c

@@ -2671,7 +2671,6 @@ enum sci_status sci_controller_complete_io(struct isci_host *ihost,
 					   struct isci_request *ireq)
 {
 	enum sci_status status;
-	u16 index;
 
 	switch (ihost->sm.current_state_id) {
 	case SCIC_STOPPING:
@@ -2682,7 +2681,6 @@ enum sci_status sci_controller_complete_io(struct isci_host *ihost,
 		if (status != SCI_SUCCESS)
 			return status;
 
-		index = ISCI_TAG_TCI(ireq->io_tag);
 		clear_bit(IREQ_ACTIVE, &ireq->flags);
 		return SCI_SUCCESS;
 	default: