Always suffix with device number in discovery topic

[emontnemery]

Prevent duplicate devices discovered if device is reconfigured.

Another option would be to do something like this to clear the retained topic:

// Clear "other" topics first in case the device has been reconfigured
    if (1 == i)
    {
      snprintf_P(stopic, sizeof(stopic), PSTR(HOME_ASSISTANT_DISCOVERY_PREFIX "/%s/%s%s/config"), (is_light) ? "switch" : "light", mqtt_topic, (1 == devices_present) ? sidx : "");
      MqttPublish(stopic, true);
      snprintf_P(stopic, sizeof(stopic), PSTR(HOME_ASSISTANT_DISCOVERY_PREFIX "/%s/%s%s/config"), (is_light) ? "light" : "switch", mqtt_topic, (1 == devices_present) ? sidx : "");
      MqttPublish(stopic, true);
    }
    snprintf_P(stopic, sizeof(stopic), PSTR(HOME_ASSISTANT_DISCOVERY_PREFIX "/%s/%s%s/config"), (is_light) ? "switch" : "light", mqtt_topic, (1 == devices_present) ? "" : sidx);
    MqttPublish(stopic, true);
    snprintf_P(stopic, sizeof(stopic), PSTR(HOME_ASSISTANT_DISCOVERY_PREFIX "/%s/%s%s/config"), (is_light) ? "light" : "switch", mqtt_topic, (1 == devices_present) ? "" : sidx);

[emontnemery]

@arendst is the patch OK, or does it need to be improved in some way?