LoRa Mac Node - OTAA

[nestorayuso]

LoRaMac-node implementation is smart enough to use default RX2 parameters during join regardless you change the RX2 parameters with:

        // Set which channel to use for RX2
        mibReq.Type = MIB_RX2_CHANNEL;
        mibReq.Param.Rx2Channel = (Rx2ChannelParams_t){869525000, DR_3};
        LoRaMacMibSetRequestConfirm(&mibReq);