ath9k: remove declarations of some nonexistant functions

int ath9k_init_device(u16 devid, struct ath_softc *sc, u16 subsysid,

		    const struct ath_bus_ops *bus_ops);

void ath9k_deinit_device(struct ath_softc *sc);

const char *ath_mac_bb_name(u32 mac_bb_version);

const char *ath_rf_name(u16 rf_version);

void ath9k_set_hw_capab(struct ath_softc *sc, struct ieee80211_hw *hw);

void ath9k_update_ichannel(struct ath_softc *sc, struct ieee80211_hw *hw,

			   struct ath9k_channel *ichan);