Extends ffpb-debug to include additional WiFi debug data.

Due to the WiFi blackout problem with ath9k devices, gluon devs request additional
debugging data from the ath9k debugfs [1]. We follow this advice and try to fetch even
more data from the debugfs for ffpb-debug.

[1] https://github.com/freifunk-gluon/gluon/issues/130