ath9k: Cleanup ineffective return values

This patch makes the return type of some of the functions
void as those functions always return true

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index ddb24c4..dd8508e 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -590,7 +590,7 @@
 void ath9k_hw_setrxfilter(struct ath_hw *ah, u32 bits);
 bool ath9k_hw_phy_disable(struct ath_hw *ah);
 bool ath9k_hw_disable(struct ath_hw *ah);
-bool ath9k_hw_set_txpowerlimit(struct ath_hw *ah, u32 limit);
+void ath9k_hw_set_txpowerlimit(struct ath_hw *ah, u32 limit);
 void ath9k_hw_setmac(struct ath_hw *ah, const u8 *mac);
 void ath9k_hw_setopmode(struct ath_hw *ah);
 void ath9k_hw_setmcastfilter(struct ath_hw *ah, u32 filter0, u32 filter1);