add tcp echo demo in nxp demo project
<name>$PROJ_DIR$\..\..\..\..\..\demos\shadow\aws_iot_demo_shadow.c</name>
</file>
</group>
+ <group>
+ <name>tcp</name>
+ <file>
+ <name>$PROJ_DIR$\..\..\..\..\..\demos\tcp\aws_tcp_echo_client_single_task.c</name>
+ </file>
+ <file>
+ <name>$PROJ_DIR$\..\..\..\..\..\demos\tcp\aws_tcp_echo_client_single_tasks.h</name>
+ </file>
+ </group>
</group>
<group>
<name>libraries</name>
