wifi_statistics: remove unused parameter from seq_printf

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
wifi_statistics: track bitrate per station

this is somewhat vague as beacons etc are counted too, but might
help to get a general feeling for the connection quality.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>