mac80211: reject zero MAC address in add station

This came up in fuzz testing, and really we don't consider
all-zeroes to be a valid MAC address in most places, so
also reject it here to avoid confusion later on.
Signed-off-by: Karthikeyan Periyasamy <periyasa@codeaurora.org>
Link: https://lore.kernel.org/r/1563959770-21570-1-git-send-email-periyasa@codeaurora.org
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1543,7 +1543,7 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
 	if (ether_addr_equal(mac, sdata->vif.addr))
 		return -EINVAL;
 
-	if (is_multicast_ether_addr(mac))
+	if (!is_valid_ether_addr(mac))
 		return -EINVAL;
 
 	sta = sta_info_alloc(sdata, mac, GFP_KERNEL);