ath9k: Fix IQ cal post processing for SoC

Calibration data is not reused for SoC chips, so
call ar9003_hw_tx_iq_cal_post_proc() with the correct
argument. The 'is_reusable' flag is currently used
only for PC-OEM chips, but it makes things clearer to
specify it explicity.

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