ath9k: Fix compilation breakage

Wrap the MCI-work canceling with CONFIG_ATH9K_BTCOEX_SUPPORT.
Reported-by: Emmanuel Benisty <benisty.e@gmail.com>
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/main.c

@@ -151,8 +151,10 @@ static void __ath_cancel_work(struct ath_softc *sc)
 	cancel_delayed_work_sync(&sc->tx_complete_work);
 	cancel_delayed_work_sync(&sc->hw_pll_work);
 
+#ifdef CONFIG_ATH9K_BTCOEX_SUPPORT
 	if (ath9k_hw_mci_is_enabled(sc->sc_ah))
 		cancel_work_sync(&sc->mci_work);
+#endif
 }
 
 static void ath_cancel_work(struct ath_softc *sc)