net: bridge: vlan: add basic option dumping support

We'll be dumping the options for the whole range if they're equal. The
first range vlan will be used to extract the options. The commit doesn't
change anything yet it just adds the skeleton for the support. The dump
will happen when the first option is added.

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