ath9k: fill channel mode in caldata

It is useful to have channel mode in caldata to find out
whether operaing channel is in HT40/20 when we are currently
on offchannel. It will be used by BTCOEX to enable/disable
concurrent tx mechanism later.

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