ath9k: port to cfg80211 rfkill

This ports the ath9k rfkill code to the new API offered by
cfg80211 and thus removes a lot of useless stuff.

("With this series a kernel panic, which is a regression, during module
unload disappears." -- Vasanthakumar Thiagarajan <vasanth@atheros.com>

Other patches in the series:

  ath9k: Add helper to get ath9k specific current channel
  ath9k: Make sure we have current channel in ah_curchan before rf
    disable/enable

-- JWL)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Luis Rodriguez <mcgrof@gmail.com>
Tested-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hw.h

@@ -565,9 +565,6 @@ u32 ath9k_hw_gpio_get(struct ath_hw *ah, u32 gpio);
 void ath9k_hw_cfg_output(struct ath_hw *ah, u32 gpio,
 			 u32 ah_signal_type);
 void ath9k_hw_set_gpio(struct ath_hw *ah, u32 gpio, u32 val);
-#if defined(CONFIG_RFKILL) || defined(CONFIG_RFKILL_MODULE)
-void ath9k_enable_rfkill(struct ath_hw *ah);
-#endif
 u32 ath9k_hw_getdefantenna(struct ath_hw *ah);
 void ath9k_hw_setantenna(struct ath_hw *ah, u32 antenna);
 bool ath9k_hw_setantennaswitch(struct ath_hw *ah,