* RAK: "start ota" now replies with Bluetooth MAC address

src/helpers/nrf52/RAK4631Board.cpp

@@ -80,6 +80,11 @@ bool RAK4631Board::startOTAUpdate(const char* id, char reply[]) {
   Bluefruit.Advertising.setFastTimeout(30);   // number of seconds in fast mode
   Bluefruit.Advertising.start(0);             // 0 = Don't stop advertising after n seconds
 
-  strcpy(reply, "OK - started");
+  uint8_t mac_addr[6];
+  memset(mac_addr, 0, sizeof(mac_addr));
+  Bluefruit.getAddr(mac_addr);
+  sprintf(reply, "OK - mac: %02X:%02X:%02X:%02X:%02X:%02X", 
+      mac_addr[0], mac_addr[1], mac_addr[2], mac_addr[3], mac_addr[4], mac_addr[5]);
+
   return true;
 }