cpuidle: menu: Use ktime_to_us instead of reinventing the wheel

The ktime_to_us implementation is slightly better than the one implemented
in menu.c. Use it

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/governors/menu.c

@@ -296,7 +296,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
 	int i;
 	unsigned int interactivity_req;
-	struct timespec t;
 
 	if (data->needs_update) {
 		menu_update(drv, dev);
@@ -310,9 +309,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 		return 0;
 
 	/* determine the expected residency time, round up */
-	t = ktime_to_timespec(tick_nohz_get_sleep_length());
-	data->next_timer_us =
-		t.tv_sec * USEC_PER_SEC + t.tv_nsec / NSEC_PER_USEC;
+	data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length());
 
 
 	data->bucket = which_bucket(data->next_timer_us);