bridge: Assign rtnl_link_ops to bridge devices created via ioctl (v2)

[ Upstream commit 149ddd83a92b02c658d6c61f3276eb6500d585e8 ]

This ensures that bridges created with brctl(8) or ioctl(2) directly
also carry IFLA_LINKINFO when dumped over netlink. This also allows
to create a bridge with ioctl(2) and delete it with RTM_DELLINK.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>