cpuidle: fix comment

Signed-off-by: NAntonio Ospite <ao2@ao2.it>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: "tuukka.tikkanen@linaro.org" <tuukka.tikkanen@linaro.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/cpuidle/governors/menu.c

@@ -406,7 +406,7 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	 *
 	 * Any measured amount of time will include the exit latency.
 	 * Since we are interested in when the wakeup begun, not when it
-	 * was completed, we must substract the exit latency. However, if
+	 * was completed, we must subtract the exit latency. However, if
 	 * the measured amount of time is less than the exit latency,
 	 * assume the state was never reached and the exit latency is 0.
 	 */