ath9k: Fix TSF Adjust usage

TSF adjust is needed only for AP mode when staggered beacons
are used. Since we support only a single interface in IBSS mode,
disable setting the TSF adjust register.
Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath9k/core.c

@@ -534,7 +534,8 @@ int ath_vap_attach(struct ath_softc *sc,
 	avp->av_opmode = opmode;
 	avp->av_bslot = -1;
 
-	ath9k_hw_set_tsfadjust(sc->sc_ah, 1);
+	if (opmode == ATH9K_M_HOSTAP)
+		ath9k_hw_set_tsfadjust(sc->sc_ah, 1);
 
 	sc->sc_vaps[if_id] = avp;
 	sc->sc_nvaps++;