添加0x9102后续数据长度自动计算

src/JT809.Protocol.Test/JT809MessageBody/JT809_0x1102Test.cs

@@ -52,7 +52,6 @@ namespace JT809.Protocol.Test.JT809MessageBody
                 Bodies = new JT809_0x1102
                 {
                     SubBusinessType = 0x1102,
-                    DataLength = 36,
                     PlateformId = "3000012345",
                     StartTime = DateTime.Parse("2020-07-08 17:46:44"),
                     EndTime = DateTime.Parse("2020-07-08 17:46:44"),

src/JT809.Protocol/MessageBody/JT809_0x1102.cs

@@ -93,13 +93,14 @@ namespace JT809.Protocol.MessageBody
         public void Serialize(ref JT809MessagePackWriter writer, JT809_0x1102 value, IJT809Config config)
         {
             writer.WriteUInt16(value.SubBusinessType);
-            writer.WriteUInt32(value.DataLength);
+            writer.Skip(4, out int subContentLengthPosition);
             writer.WriteStringPadRight(value.PlateformId, 11);
             writer.WriteUTCDateTime(value.StartTime);
             writer.WriteUTCDateTime(value.EndTime);
             writer.WriteUInt32(value.LoseDymamicSum);
             writer.WriteByte(value.DisconnectNum);
             writer.WriteUInt32(value.DisconnectTime);
+            writer.WriteInt32Return(writer.GetCurrentPosition() - subContentLengthPosition - 4, subContentLengthPosition);
         }
     }
 }