ath9k: remove support for the FIF_PROMISC_IN_BSS filter flag

The hardware rx filter flag triggered by FIF_PROMISC_IN_BSS is overly broad
and covers even frames with PHY errors. When this flag is enabled, this message
shows up frequently during scanning or hardware resets:

ath: Could not stop RX, we could be confusing the DMA engine when we start RX up

Since promiscuous mode is usually not particularly useful, yet enabled by
default by bridging (either used normally in 4-addr mode, or with hacks
for various virtualization software), we should sacrifice it for better
reliability during normal operation.

This patch leaves it enabled if there are active monitor mode interfaces, since
it's very useful for debugging.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index cb559e3..a9c3f46 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -413,9 +413,7 @@
 	 * 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->is_monitoring))
+	if (sc->sc_ah->is_monitoring)
 		rfilt |= ATH9K_RX_FILTER_PROM;
 
 	if (sc->rx.rxfilter & FIF_CONTROL)