Change pihole interface if needed

src/freedombone-app-pihole

         return
     fi
 
+    if [[ $(config_param_exists WIFI_INTERFACE) == "0" ]]; then
+        PIHOLE_IFACE=eth0
+    else
+        read_config_param WIFI_INTERFACE
+        PIHOLE_IFACE=$WIFI_INTERFACE
+        write_config_param "PIHOLE_IFACE" "$PIHOLE_IFACE"
+    fi
+
     IPv4_address=$(get_ipv4_address)
     IPv6_address=$(get_ipv6_address)