ath5k: cleanup channel to eprom_mode function

Stop returning negative values from ath5k_eeprom_mode_from_channel.
Yell loudly about that case in that function instead and return the
default/zero/mode A. This cleans up the callers, but needs to pass ah
down to ath5k_eeprom_mode_from_channel for ATH5K_WARN. For that
purpose we also need the declaration to be moved to ath5k.h.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/ath5k.h

@@ -1523,7 +1523,8 @@ int ath5k_hw_dma_stop(struct ath5k_hw *ah);
 /* EEPROM access functions */
 int ath5k_eeprom_init(struct ath5k_hw *ah);
 void ath5k_eeprom_detach(struct ath5k_hw *ah);
-
+int ath5k_eeprom_mode_from_channel(struct ath5k_hw *ah,
+		struct ieee80211_channel *channel);
 
 /* Protocol Control Unit Functions */
 /* Helpers */