bridge: allow creating bridge devices with netlink

Add netlink device ops to allow creating bridge device via netlink.
This works in a manner similar to vlan, macvlan and bonding.

Example:
  # ip link add link dev br0 type bridge
  # ip link del dev br0

The change required rearranging initializtion code to deal with
being called by create link. Most of the initialization happens
in br_dev_setup, but allocation of stats is done in ndo_init callback
to deal with allocation failure. Sysfs setup has to wait until
after the network device kobject is registered.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_notify.c b/net/bridge/br_notify.c
index 7d337c9..7a03bb9 100644
--- a/net/bridge/br_notify.c
+++ b/net/bridge/br_notify.c
@@ -36,6 +36,12 @@
 	struct net_bridge *br;
 	int err;
 
+	/* register of bridge completed, add sysfs entries */
+	if ((dev->priv_flags && IFF_EBRIDGE) && event == NETDEV_REGISTER) {
+		br_sysfs_addbr(dev);
+		return NOTIFY_DONE;
+	}
+
 	/* not a port of a bridge */
 	p = br_port_get_rtnl(dev);
 	if (!p)