wifi: mac80211: clear vif drv_priv after remove_interface when stopping

Avoid reusing stale driver data when an interface is brought down and up
again. In order to avoid having to duplicate the memset in every single
driver, do it here.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://patch.msgid.link/20240704130947.48609-1-nbd@nbd.nameSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/iface.c

@@ -689,8 +689,12 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do
 
 		fallthrough;
 	default:
-		if (going_down)
+		if (!going_down)
+			break;
 		drv_remove_interface(local, sdata);
+
+		/* Clear private driver data to prevent reuse */
+		memset(sdata->vif.drv_priv, 0, local->hw.vif_data_size);
 	}
 
 	ieee80211_recalc_ps(local);