time: Implement timespec_add

After accidentally misusing timespec_add_safe, I wanted to make sure
we don't accidently trip over that issue again, so I created a simple
timespec_add() function which we can use to replace the instances
of timespec_add_safe() that don't want the overflow detection.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1279068988-21864-3-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index caf8d4d..623fe3d 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -579,9 +579,9 @@
 
 	if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
 		ts = timespec_sub(ts, timekeeping_suspend_time);
-		xtime = timespec_add_safe(xtime, ts);
+		xtime = timespec_add(xtime, ts);
 		wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
-		total_sleep_time = timespec_add_safe(total_sleep_time, ts);
+		total_sleep_time = timespec_add(total_sleep_time, ts);
 	}
 	/* re-base the last cycle value */
 	timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
@@ -887,7 +887,7 @@
  */
 void monotonic_to_bootbased(struct timespec *ts)
 {
-	*ts = timespec_add_safe(*ts, total_sleep_time);
+	*ts = timespec_add(*ts, total_sleep_time);
 }
 EXPORT_SYMBOL_GPL(monotonic_to_bootbased);