Create a max_time too

This is helpful for matching with min_time.

Change-Id: I247a43027777843f1d3fe41ed8b857abc1a80a54
diff --git a/aos/time/time.cc b/aos/time/time.cc
index 29b2956..7661daf 100644
--- a/aos/time/time.cc
+++ b/aos/time/time.cc
@@ -135,7 +135,9 @@
 }  // namespace time
 
 constexpr monotonic_clock::time_point monotonic_clock::min_time;
+constexpr monotonic_clock::time_point monotonic_clock::max_time;
 constexpr realtime_clock::time_point realtime_clock::min_time;
+constexpr realtime_clock::time_point realtime_clock::max_time;
 
 monotonic_clock::time_point monotonic_clock::now() noexcept {
 #ifdef __linux__