net/mlx5: fix VLAN match for DV mode

net/mlx5: fix VLAN match for DV mode

Currently MLX5 PMD can't match on untagged packets specifically.
Tagged traffic still hits the flows intended for untagged packets.
If the flow has ETH, it will catch all matching packets, tagged
and untagged.
The solution is to use cvlan_tag bit.
If mask=1 and value=0 it matches on untagged traffic.
If mask=1 and value=1 it matches on tagged traffic.
This is the kernel implementation.

This patch updated MLX5 PMD to set cvlan_tag mask and value according
to flow rule contents.
This update is relevant when using DV flow engine (dv_flow_en=1).

See example at https://doc.dpdk.org/guides/nics/mlx5.html#limitations.

Fixes: fc2c498ccb94 ("net/mlx5: add Direct Verbs translate items")
Cc: stable@dpdk.org
Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>