ath9k: Simplify ANI initialization

The check "enable_ani" is not required since it is always
set to true and the logic for disabling/enabling ANI via
debugfs is done at a higher layer.

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