dm thin: use time_is_before_jiffies instead of open coding it

Use time_is_before_jiffies() to improve code readability.
Signed-off-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-thin.c

@@ -161,7 +161,7 @@ static void throttle_work_start(struct throttle *t)
 
 static void throttle_work_update(struct throttle *t)
 {
-	if (!t->throttle_applied && jiffies > t->threshold) {
+	if (!t->throttle_applied && time_is_before_jiffies(t->threshold)) {
 		down_write(&t->lock);
 		t->throttle_applied = true;
 	}