net/mlx5: support match on GTP flags

This patch adds to MLX5 PMD the support of matching on
GTP header item v_pt_rsv_flags.

This item is contained in 1 byte of the format:
-------------------------------------------
| bit   | 0 - 2   | 3  | 4   | 5 | 6 | 7  |
|-----------------------------------------|
| value | Version | PT | Res | E | S | PN |
-------------------------------------------

Matching is supported only for GTP flags E, S, PN.
Therefore values 0 to 7 are supported.

Mask must be set accordingly:
... gtp v_pt_rsv_flags is 1 v_pt_rsv_flags mask 0x07 ...

Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>