net: bridge: vlan: add rtm range support

Add a new vlandb nl attribute - BRIDGE_VLANDB_ENTRY_RANGE which causes
RTM_NEWVLAN/DELVAN to act on a range. Dumps now automatically compress
similar vlans into ranges. This will be also used when per-vlan options
are introduced and vlans' options match, they will be put into a single
range which is encapsulated in one netlink attribute. We need to run
similar checks as br_process_vlan_info() does because these ranges will
be used for options setting and they'll be able to skip
br_process_vlan_info().

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