netfilter: flowtable: bridge vlan hardware offload and switchdev

The switch might have already added the VLAN tag through PVID hardware
offload. Keep this extra VLAN in the flowtable but skip it on egress.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>