ath9k_htc: configure bssid on ASSOC/IBSS change

After the change "mac80211: remove spurious BSSID change flag",
BSS_CHANGED_BSSID will not be passed on association or IBSS
status changes. So it could be better to program bssid on ASSOC
or IBSS change notification. Not doing so, is affecting the
packet transmission.

Cc: stable@vger.kernel.org [3.4+]
Reported-by: Michael Leun <lkml20120218@newton.leun.net>
Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>