Configure LoRA gateway parameters at startup (#1234)

Without this (and without sending an initial MQTT message to the gateway
to configure it) messages are not necessarily received if parameters are
different from firmware defaults.

This patch helped at least two users:
- https://community.home-assistant.io/t/awesome-lora-soil-sensor/304351/23
- https://community.home-assistant.io/t/awesome-lora-soil-sensor/304351/18

Change-Id: Ia65ee5780b56f81fc73662c8779b79083805009b

Co-authored-by: Grégoire Seux <grego_openmqttgateway@familleseux.net>

main/ZgatewayLORA.ino

@@ -49,6 +49,12 @@ void setupLORA() {
   Log.notice(F("LORA_SS: %d" CR), LORA_SS);
   Log.notice(F("LORA_RST: %d" CR), LORA_RST);
   Log.notice(F("LORA_DI0: %d" CR), LORA_DI0);
+  LoRa.setTxPower(LORA_TX_POWER);
+  LoRa.setSpreadingFactor(LORA_SPREADING_FACTOR);
+  LoRa.setSignalBandwidth(LORA_SIGNAL_BANDWIDTH);
+  LoRa.setCodingRate4(LORA_CODING_RATE);
+  LoRa.setPreambleLength(LORA_PREAMBLE_LENGTH);
+  LoRa.setSyncWord(LORA_SYNC_WORD);
   Log.trace(F("ZgatewayLORA setup done" CR));
 }