prometheus-node-exporter-lua: wifi packets should be a counter

These output a count of the number of packets transmitted/received, so
should be tracked as a counter. As it stands, promtool is warning that
these shouldn't be named ending _total if they're a gauge.

Signed-off-by: Alex Tomlins <alex@tomlins.org.uk>

utils/prometheus-node-exporter-lua/files/usr/lib/lua/prometheus-collectors/wifi_stations.lua

@@ -3,8 +3,8 @@ local iwinfo = require "iwinfo"
 
 local function scrape()
   local metric_wifi_station_signal = metric("wifi_station_signal_dbm","gauge")
-  local metric_wifi_station_tx_packets = metric("wifi_station_tx_packets_total","gauge")
-  local metric_wifi_station_rx_packets = metric("wifi_station_rx_packets_total","gauge")
+  local metric_wifi_station_tx_packets = metric("wifi_station_tx_packets_total","counter")
+  local metric_wifi_station_rx_packets = metric("wifi_station_rx_packets_total","counter")
 
   local u = ubus.connect()
   local status = u:call("network.wireless", "status", {})