bridge: fix accidental creation of sysfs directory

Commit bb900b27

 ("bridge: allow
creating bridge devices with netlink") introduced a bug in net-next
because of a typo in notifier. Every device would have the sysfs
bridge directory (and files).

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>