s390/cio: Use array indices instead of pointer arithmetic

ccw_device_get_ciw() already uses array indices to iterate over the vector
of CIWs, but then switches to pointer arithmetic when returning the one it
found. Change this to make it more consistent.

Signed-off-by: Benjamin Block <[e-mail]>
Reviewed-by: Vineeth Vijayan <[e-mail]>
Signed-off-by: Alexander Gordeev <[e-mail]>

drivers/s390/cio/device_ops.c

···
 		return NULL;
 	for (ciw_cnt = 0; ciw_cnt < MAX_CIWS; ciw_cnt++)
 		if (cdev->private->dma_area->senseid.ciw[ciw_cnt].ct == ct)
-			return cdev->private->dma_area->senseid.ciw + ciw_cnt;
+			return &cdev->private->dma_area->senseid.ciw[ciw_cnt];
 	return NULL;
 }