wireless: add back sysfs directory

commit 35b2a113cb0298d4f9a1263338b456094a414057 broke (at least)
Fedora's networking scripts, they check for the existence of the
wireless directory. As the files aren't used, add the directory
back and not the files. Also do it for both drivers based on the
old wireless extensions and cfg80211, regardless of whether the
compat code for wext is built into cfg80211 or not.

Cc: stable@vger.kernel.org [3.6]
Reported-by: Dave Airlie <airlied@gmail.com>
Reported-by: Bill Nottingham <notting@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/core/net-sysfs.c

@@ -429,6 +429,17 @@ static struct attribute_group netstat_group = {
 	.name  = "statistics",
 	.attrs  = netstat_attrs,
 };
+
+#if IS_ENABLED(CONFIG_WIRELESS_EXT) || IS_ENABLED(CONFIG_CFG80211)
+static struct attribute *wireless_attrs[] = {
+	NULL
+};
+
+static struct attribute_group wireless_group = {
+	.name = "wireless",
+	.attrs = wireless_attrs,
+};
+#endif
 #endif /* CONFIG_SYSFS */
 
 #ifdef CONFIG_RPS
@@ -1409,6 +1420,15 @@ int netdev_register_kobject(struct net_device *net)
 		groups++;
 
 	*groups++ = &netstat_group;
+
+#if IS_ENABLED(CONFIG_WIRELESS_EXT) || IS_ENABLED(CONFIG_CFG80211)
+	if (net->ieee80211_ptr)
+		*groups++ = &wireless_group;
+#if IS_ENABLED(CONFIG_WIRELESS_EXT)
+	else if (net->wireless_handlers)
+		*groups++ = &wireless_group;
+#endif
+#endif
 #endif /* CONFIG_SYSFS */
 
 	error = device_add(dev);