net/mlx5: support ESP SPI match and RSS hash

net/mlx5: support ESP SPI match and RSS hash

In packets with ESP header, the inner IP will be encrypted, and
its fields cannot be used for RSS hashing. So, ESP packets
can be hashed only by the outer IP layer.
So, when using RSS on ESP packets, hashing may not be efficient,
because the fields used by the hash functions are only the outer IPs,
causing all traffic belonging to all tunnels between a given
pair of GWs to land on one core.
Adding the SPI hash field can extend the spreading of IPsec packets.

Signed-off-by: Raja Zidane <rzidane@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>