net: bridge: vlan: add support for dumping global vlan options

Add a new vlan options dump flag which causes only global vlan options
to be dumped. The dumps are done only with bridge devices, ports are
ignored. They support vlan compression if the options in sequential
vlans are equal (currently always true).

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