ath5k: make ath5k_update_bssid_mask_and_opmode() static

This fixes this sparse warning:

  CHECK   drivers/net/wireless/ath/ath5k/base.c
drivers/net/wireless/ath/ath5k/base.c:569:6: warning: symbol
'ath5k_update_bssid_mask_and_opmode' 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/ath5k/base.c

@@ -566,7 +566,7 @@ static void ath_do_set_opmode(struct ath5k_softc *sc)
 		  sc->opmode, ath_opmode_to_string(sc->opmode));
 }
 
-void ath5k_update_bssid_mask_and_opmode(struct ath5k_softc *sc,
+static void ath5k_update_bssid_mask_and_opmode(struct ath5k_softc *sc,
 					       struct ieee80211_vif *vif)
 {
 	struct ath_common *common = ath5k_hw_common(sc->ah);