ath9k: Fix MCI cleanup

We are doing MCI cleanup eventhough BTCOEX is not enabled
via module parameter. This means we do ath_mci_cleanup
though we skipped calling ath_mci_setup. Yet it does not
causes any issues now  as we free the DMA buffer allocated
only when it is allocated during ath_mci_setup.

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