raid5: delete unnecessary warnning

If device has R5_LOCKED set, it's legit device has R5_SkipCopy set and page !=
orig_page. After R5_LOCKED is clear, handle_stripe_clean_event will clear the
SkipCopy flag and set page to orig_page. So the warning is unnecessary.
Reported-by: NJoey Liao <joeyliao@qnap.com>
Signed-off-by: NShaohua Li <shli@fb.com>

drivers/md/raid5.c

@@ -3502,8 +3502,6 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 				dev = &sh->dev[i];
 			} else if (test_bit(R5_Discard, &dev->flags))
 				discard_pending = 1;
-			WARN_ON(test_bit(R5_SkipCopy, &dev->flags));
-			WARN_ON(dev->page != dev->orig_page);
 		}
 
 	r5l_stripe_write_finished(sh);