sysfs -- don't crash if removing non-existant attribute group

Some (buggy) network drivers in 2.6 decide to set the statistics hook, after registration. This causes unregister_netdevice to crash because it attempts to remove the 'statistics' attribute group it thought was created.

This fixes sysfs so it ignores the problem. Another set of patches will address the remaining buggy ether drivers.

diff -Nru a/fs/sysfs/group.c b/fs/sysfs/group.c
@@ -65,9 +65,11 @@
 {
 	struct dentry * dir;
 
-	if (grp->name)
+	if (grp->name) {
 		dir = sysfs_get_dentry(kobj->dentry,grp->name);
-	else
+		if (dir == NULL)	/* non-existent */
+			return;
+	} else
 		dir = kobj->dentry;
 
 	remove_files(dir,grp);

Please change this patch to add a net_ratelimit()'d warning message so that we can catch new instances of this problem.

Thanks.