wifi_files: TX MCS rates and client movement

1. Output information about the TX MCS rate and NSS.
   Note that not all chipsets get this right, for example
   ath10k always sends 0 for its 802.11ac MCS and NSS.

2. If a client moves from one interface to another, clear
   the client_state_t. Otherwise the counters will be
   screwy, like saying the max width seen on 2.4 GHz is
   80MHz (when really the 80MHz is leftover from when the
   client was on 5GHz).

Change-Id: Ib40f3e4570e0b614121cd01b3a3c502d1ba51314
1 file changed