aos/sctp: Add server partial delivery stats

Change-Id: I63439180ddf2523a73c2bc579fe4ce2a6574dc67
diff --git a/aos/network/message_bridge_server.fbs b/aos/network/message_bridge_server.fbs
index fa73ba5..cdf970c 100644
--- a/aos/network/message_bridge_server.fbs
+++ b/aos/network/message_bridge_server.fbs
@@ -19,7 +19,7 @@
   // Number of packets that have been dropped (if known).
   dropped_packets:uint (id: 2);
 
-  // Number of packets received on all channels.
+  // Number of packets sent on all channels.
   sent_packets:uint (id: 3);
 
   // This is the measured monotonic offset for the connected node in
@@ -30,6 +30,10 @@
   // Boot UUID of the client.
   boot_uuid:string (id: 5);
 
+  // Number of extra calls needed to receive a single message
+  // (indicates congestion)
+  partial_deliveries:uint (id: 6);
+
   // TODO(austin): Per channel counts?
 }