bridge: Separate egress policy bitmap

Add an ability to configure a separate "untagged" egress
policy to the VLAN information of the bridge.  This superseeds PVID
policy and makes PVID ingress-only.  The policy is configured with a
new flag and is represented as a port bitmap per vlan.  Egress frames
with a VLAN id in "untagged" policy bitmap would egress
the port without VLAN header.

Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>