net/mlx5: fix GRE protocol type translation for Verbs

net/mlx5: fix GRE protocol type translation for Verbs

When application creates several flows to match on GRE tunnel without
explicitly specifying GRE protocol type value in flow rules, PMD will
translate that to zero mask.
RDMA-CORE cannot distinguish between different inner flow types and
produces identical matchers for each zero mask.

The patch extracts inner header type from flow rule and forces it in
GRE protocol type, if application did not specify any.

Fixes: 84c406e74524 ("net/mlx5: add flow translate function")
Cc: stable@dpdk.org
Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>