ath9k_hw: Fix calibration for AR9340

TX_IQ_ON_AGC_CAL should not be enabled for AR9340. TX-IQ calibration
is run as part of AGC calibration only for AR9485, AR9462 and AR9565.
For the others (AR9300, AR9330, AR9340), TX-IQ cal is done independent
of AGC-cal.

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