cfg80211: correct bridge/4addr mode check

Without the patch we fail:

$ sudo brctl addbr br0
$ sudo brctl addif br0 wlp1s0
$ sudo iw wlp1s0 set 4addr on
command failed: Device or resource busy (-16)

Last command failed but iface was already in 4addr mode.

Fixes: ad4bb6f8 ("cfg80211: disallow bridging managed/adhoc interfaces")
Signed-off-by: Janusz Dziedzic <janusz.dziedzic@gmail.com>
Link: https://lore.kernel.org/r/20211024201546.614379-1-janusz.dziedzic@gmail.com
[add fixes tag, fix indentation, edit commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/util.c

@@ -1028,14 +1028,14 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev,
 	    !(rdev->wiphy.interface_modes & (1 << ntype)))
 		return -EOPNOTSUPP;
 
-	/* if it's part of a bridge, reject changing type to station/ibss */
-	if (netif_is_bridge_port(dev) &&
-	    (ntype == NL80211_IFTYPE_ADHOC ||
-	     ntype == NL80211_IFTYPE_STATION ||
-	     ntype == NL80211_IFTYPE_P2P_CLIENT))
-		return -EBUSY;
-
 	if (ntype != otype) {
+		/* if it's part of a bridge, reject changing type to station/ibss */
+		if (netif_is_bridge_port(dev) &&
+		    (ntype == NL80211_IFTYPE_ADHOC ||
+		     ntype == NL80211_IFTYPE_STATION ||
+		     ntype == NL80211_IFTYPE_P2P_CLIENT))
+			return -EBUSY;
+
 		dev->ieee80211_ptr->use_4addr = false;
 		dev->ieee80211_ptr->mesh_id_up_len = 0;
 		wdev_lock(dev->ieee80211_ptr);