ath9k: Fix eifs/usec timeout for AR9287 v1.3+

For AR9287 v1.3+ chips, MAC runs at 117MHz. But the initvals
IFS parameters are loaded based on 44/88MHz clockrate. So
eifs/usec from ini should not be used for AR9287 v1.3+.
The mentioned values are tested on 2 chain HT40 mode.

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