bridge: support for multiple vlans and vlan ranges in setlink and dellink requests

This patch changes bridge IFLA_AF_SPEC netlink attribute parser to
look for more than one IFLA_BRIDGE_VLAN_INFO attribute. This allows
userspace to pack more than one vlan in the setlink msg.

The dumps were already sending more than one vlan info in the getlink msg.

This patch also adds bridge_vlan_info flags BRIDGE_VLAN_INFO_RANGE_BEGIN and
BRIDGE_VLAN_INFO_RANGE_END to indicate start and end of vlan range

This patch also deletes unused ifla_br_policy.

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>