sysfs: Add support for tagged directories with untagged members.

I had hopped to avoid this but the bonding driver adds a file
to /sys/class/net/  and the easiest way to handle that file is
to make it untagged and to register it only once.

So relax the rules on tagged directories, and make bonding work.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>