net/mlx5: support integrity flow item

net/mlx5: support integrity flow item

MLX5 PMD supports the following integrity filters for outer and
inner network headers:
- l3_ok
- l4_ok
- ipv4_csum_ok
- l4_csum_ok

`level` values 0 and 1 reference outer headers.
`level` > 1 reference inner headers.

Flow rule items supplied by application must explicitly specify
network headers referred by integrity item. For example:
flow create 0 ingress
  pattern
    integrity level is 0 value mask l3_ok value spec l3_ok /
    eth / ipv6 / end …

or

flow create 0 ingress
  pattern
    integrity level is 0 value mask l4_ok value spec 0 /
    eth / ipv4 proto is udp / end …

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>