ath9k: Fix FastChannelChange for AR9462/AR9565

Right now, even though these chips support cross-band
FCC, the code is non-functional since we bail out early if
the channelFlags differ. Fix this so that cross-band
FCC works for cards that support this feature.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>