mac80211: fix broadcast frame handling for 4-addr AP VLANs

Without this patch, broadcast frames from the station behind a
4-addr AP VLAN would be reflected back to the source.
Fix this by checking the 4-addr flag before bridging multicast
frames in the cell.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 006cf89..6bce97e 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1236,7 +1236,7 @@
 	if ((sdata->vif.type == NL80211_IFTYPE_AP ||
 	     sdata->vif.type == NL80211_IFTYPE_AP_VLAN) &&
 	    !(sdata->flags & IEEE80211_SDATA_DONT_BRIDGE_PACKETS) &&
-	    (rx->flags & IEEE80211_RX_RA_MATCH)) {
+	    (rx->flags & IEEE80211_RX_RA_MATCH) && !rx->sdata->use_4addr) {
 		if (is_multicast_ether_addr(ehdr->h_dest)) {
 			/*
 			 * send multicast frames both to higher layers in