net/mlx5: fix tunnel offloads cap query

net/mlx5: fix tunnel offloads cap query

The query for the tunnel stateless offloads is wrongly implemented
because of:

1. It was using the device id to query for the offloads.
2. It was using a compilation flag for Verbs which no longer exits.

The main reason was lack of proper API from Verbs.

Fixing the query to use rdma-core API. The capability returned from
rdma-core refer to both Tx and Rx sides.
Eventhough there is a separate cap for GRE and VXLAN, implementation merge
them into a single flag in order to simplify the checks on the data
path.

Fixes: 43e9d9794cde ("net/mlx5: support upstream rdma-core")
Fixes: f5fde5205101 ("net/mlx5: add hardware checksum offload for tunnel packets")
Cc: stable@dpdk.org
Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
Acked-by: Yongseok Koh <yskoh@mellanox.com>
Acked-by: Xueming Li <xuemingl@mellanox.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>