Add ids to flatbuffer fields in y2012, y2016, frc971, and aos

Change-Id: I9ed9006ce6224e2df0459df47771786b928164a1
diff --git a/aos/network/timestamp.fbs b/aos/network/timestamp.fbs
index 299ecaf..ccd7f40 100644
--- a/aos/network/timestamp.fbs
+++ b/aos/network/timestamp.fbs
@@ -3,13 +3,13 @@
 namespace aos.message_bridge;
 
 table ClientOffset {
-  node:Node;
+  node:Node (id: 0);
 
-  monotonic_offset:int64;
+  monotonic_offset:int64 (id: 1);
 }
 
 table Timestamp {
-  offsets:[ClientOffset];
+  offsets:[ClientOffset] (id: 0);
 }
 
 root_type Timestamp;