pw_bluetooth: Add AVDTP_START_CMD

Bug: 381291639

Change-Id: I9014500cd0dd0fbf27f1c6306d1f3a14e26f67f6
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/259354
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Docs-Not-Needed: Charlie Boutier <charliebout@google.com>
Commit-Queue: Charlie Boutier <charliebout@google.com>
Reviewed-by: Ben Lawson <benlawson@google.com>

pw_bluetooth/public/pw_bluetooth/avdtp.emb

@@ -273,6 +273,34 @@ struct SetConfigurationReject:
   $next [+1]  ServiceCategory  service_category
   $next [+1]  ErrorCode        error_code
 
+# Cf 8.13 Start Stream
+
+
+struct StreamStartCommand:
+  -- Cf 8.13.1 AVDTP_START_CMD
+  [requires: signaling_header.message_type == MessageType.COMMAND && signaling_header.signal_identifier == SignalIdentifierCode.AVDTP_START]
+  0     [+2]         SignalingHeader  signaling_header
+  $next [+1]  bits:
+    0     [+6]       Seid             acp_seid
+    $next [+2]       UInt             rfa
+
+
+struct StreamStartResponse:
+  -- Cf 8.13.2 AVDTP_START_RSP
+  [requires: signaling_header.message_type == MessageType.RESPONSE_ACCEPT && signaling_header.signal_identifier == SignalIdentifierCode.AVDTP_START]
+  0 [+2]  SignalingHeader  signaling_header
+
+
+struct StreamStartReject:
+  -- Cf 8.13.3 AVDTP_START_REJ
+  [requires: signaling_header.message_type == MessageType.RESPONSE_REJECT && signaling_header.signal_identifier == SignalIdentifierCode.AVDTP_START]
+  0     [+2]         SignalingHeader  signaling_header
+  $next [+1]  bits:
+    0     [+6]       Seid             acp_seid
+    $next [+2]       UInt             rfa
+
+  $next [+1]         ErrorCode        error_code
+
 # Cf 8.14 Stream Release