ath9k: fix ANI operation in AP mode

ath9k_ani_reset (which is called at reset time) uses a state variable
ani->update_ani to prevent the ANI noise immunity state on the operating
channel from being overwritten by background scans. Unfortunately this
is also being set for AP mode, since it's mixed with code that is only
supposed to change the default settings after a reset.

In AP mode this has the side effect of having ANI run, but being unable to
change its runtime noise immunity level, making it effectively useless.

Fix this by getting rid of ani->update_ani and passing a parameter to
ath9k_hw_set_ofdm_nil and ath9k_hw_set_cck_nil instead.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>