ath9k_hw: make use of the wrapper to check for MCI init

ath9k_hw_mci_is_enabled wrapper also takes care of
ATH9K_HW_CAP_MCI being set for the AR9462 under test.

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>