Paject Reject due to Power RF

Issue as below

Sat Feb 29 08:10:26 2020 daemon.info lora_pkt_fwd[30684]: RXTX~ {"txpk": 
{"imme":false,"tmst":510528462,"freq":923.9,"rfch":0,"powe":17,"modu":"LORA","datr":"SF7BW500","codr":"4/5","ipol":true,"size":17,"ncrc":true,"data":"IKnZOasAq17SeIpOQc0ZzBQ="}}
Sat Feb 29 08:10:26 2020 daemon.info lora_pkt_fwd[30684]: ERROR~ Packet REJECTED, unsupported RF power for TX - 17

This is due to the lorawan server use a power that the gateway not yet configured.

User can find the related region file in /etc/lora/cfg and change the parameter to support the power. for example to support 17, user can change:

"tx_lut_9": {
  "desc": "TX gain table, index 9",
  "pa_gain": 2,
  "mix_gain": 10,
  "rf_power": 14,     ----> Change this to 17 and will work. 
  "dig_gain": 0
 },