Fix infinite loop in semaphore.sem.wakeWaiters().

PiperOrigin-RevId: 300845134

pkg/sentry/kernel/semaphore/semaphore.go

@@ -554,6 +554,7 @@ func (s *sem) wakeWaiters() {
 	for w := s.waiters.Front(); w != nil; {
 		if s.value < w.value {
 			// Still blocked, skip it.
+			w = w.Next()
 			continue
 		}
 		w.ch <- struct{}{}