netxduo: Can be fetched as a component

Azure RTOS NetX Duo can now be fetched as an Open IoT SDK
component by listing it in `IOTSDK_FETCH_LIST`.
The following libraries can be built: This includes: `nextduo`,
`iot_security_module`, `asc_security_core`, and `flatccrt`.

Signed-off-by: Hugues Kamba-Mpiana <hugues.kambampiana@arm.com>