net/mlx5: fix build with rdma-core v19

net/mlx5: fix build with rdma-core v19

The flow counter support introduced by
commit 9a761de8ea14 ("net/mlx5: flow counter support") was intend to
work only with MLNX_OFED_4.3 as the upstream rdma-core
libraries were lack such support.

On rdma-core v19 the support for the flow counters was added but with
different user APIs, hence causing compilation issues on the PMD.

This patch fix the compilation errors by forcing the flow counters
to be enabled only with MLNX_OFED APIs.
Once MLNX_OFED and rdma-core APIs will be aligned, a proper patch to
support the new API will be submitted.

Fixes: 9a761de8ea14 ("net/mlx5: flow counter support")
Cc: stable@dpdk.org
Reported-by: Stephen Hemminger <stephen@networkplumber.org>
Reported-by: Ferruh Yigit <ferruh.yigit@intel.com>
Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
Acked-by: Ori Kam <orika@mellanox.com>