net/mlx5: Bridge, pop VLAN on egress table miss

Create lowest priority flow group in egress table with single rule that
matches on special reg_c1 value that is set on ingress VLAN push with
single action that pops VLAN. The flow destination is skip table that is
used to skip any further processing of packet in FDB bridge priority.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>