add Semtech SX1302 CoreCell CN490 to chirpstack-concentratord

[blockchain4trust]

sx1302c490gw1_cn490.zip

China occupies more than 50% of the LoRa market, and more and more developers are making gateways based on sx1302. It is strange that there is no CN490 option in ChirpStack Concentratord.

For this, I have added the sx1302c490gw1_cn490.rs file（this attach file), hoping that the next version of ChirpStack Concentratord will add the CN490 band. Let more Chinese users use ChirpStack, enrich the community, and exert greater influence.