[SCSI] zfcp: optimize zfcp_qdio_account

Remove expensive ktime_get()/ktime_us_delta() functions from the hot
path and use get_clock_monotonic() instead. This elimates seven
function calls and avoids a lot of unnecessary calculations.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index cc98eea..7da2fad 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/drivers/s390/scsi/zfcp_def.h
@@ -438,7 +438,7 @@
 	struct zfcp_qdio_queue	req_q;
 	spinlock_t		stat_lock;
 	spinlock_t		req_q_lock;
-	ktime_t			req_q_time;
+	unsigned long long	req_q_time;
 	u64			req_q_util;
 	atomic_t		req_q_full;
 	wait_queue_head_t	req_q_wq;