ath: make ath_hw_keysetmac() static

This fixes this sparse warning:

  CHECK   drivers/net/wireless/ath/key.c
drivers/net/wireless/ath/key.c:70:6: warning: symbol 'ath_hw_keysetmac' was not declared. Should it be static?
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/key.c

@@ -67,7 +67,8 @@ bool ath_hw_keyreset(struct ath_common *common, u16 entry)
 }
 EXPORT_SYMBOL(ath_hw_keyreset);
 
-bool ath_hw_keysetmac(struct ath_common *common, u16 entry, const u8 *mac)
+static bool ath_hw_keysetmac(struct ath_common *common,
+			     u16 entry, const u8 *mac)
 {
 	u32 macHi, macLo;
 	u32 unicast_flag = AR_KEYTABLE_VALID;