Account for socketcan providing realtime timestamps

We are getting realtime timestamps back, but were treating them as
monotonic times. Fix that.

Change-Id: Ib92ced05870dcfa7a476ce2509b28eb307bda5ac
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/frc971/can_logger/asc_logger.h b/frc971/can_logger/asc_logger.h
index 2be2eb2..e7d4e74 100644
--- a/frc971/can_logger/asc_logger.h
+++ b/frc971/can_logger/asc_logger.h
@@ -25,7 +25,7 @@
   static void WriteHeader(std::ostream &file,
                           aos::realtime_clock::time_point start_time);
 
-  std::optional<aos::monotonic_clock::time_point> first_frame_monotonic_;
+  std::optional<aos::realtime_clock::time_point> first_frame_realtime_;
 
   std::ofstream output_;