bridge: netlink: add support for vlan_filtering attribute

This patch adds the ability to toggle the vlan filtering support via
netlink. Since we're already running with rtnl in .changelink() we don't
need to take any additional locks.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>