ath9k: Fix FIF_PROMISC_IN_BSS processing in station mode

We must not disable ACK sending in this case since it would break
normal station operations. In addition, clarify the comment about AP
mode to make more sense.
Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath9k/recv.c

@@ -385,14 +385,15 @@ u32 ath_calcrxfilter(struct ath_softc *sc)
 	if (sc->sc_ah->opmode != NL80211_IFTYPE_STATION)
 		rfilt |= ATH9K_RX_FILTER_PROBEREQ;
 
-	/* Can't set HOSTAP into promiscous mode */
+	/*
+	 * Set promiscuous mode when FIF_PROMISC_IN_BSS is enabled for station
+	 * mode interface or when in monitor mode. AP mode does not need this
+	 * since it receives all in-BSS frames anyway.
+	 */
 	if (((sc->sc_ah->opmode != NL80211_IFTYPE_AP) &&
 	     (sc->rx.rxfilter & FIF_PROMISC_IN_BSS)) ||
-	    (sc->sc_ah->opmode == NL80211_IFTYPE_MONITOR)) {
+	    (sc->sc_ah->opmode == NL80211_IFTYPE_MONITOR))
 		rfilt |= ATH9K_RX_FILTER_PROM;
-		/* ??? To prevent from sending ACK */
-		rfilt &= ~ATH9K_RX_FILTER_UCAST;
-	}
 
 	if (sc->rx.rxfilter & FIF_CONTROL)
 		rfilt |= ATH9K_RX_FILTER_CONTROL;