ath9k: Disable cross-band FCC

Fast Channel Change across bands was enabled for
AR9462 recently, but this is causing baseband issues.
Disable it until this feature is tested well. Also,
remove the feature bit for AR9565 since it is
a single-band card and doesn't support this feature.

Cc: stable@vger.kernel.org
Reported-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>