net/mlx5: fix flow split combined with counter

net/mlx5: fix flow split combined with counter

Currently, for a flow containing a count action, if flow is split to
sub-flows, a new counter will be created for each sub-flow.
However only the counter created for the last sub-flow will be queried
on flow query and cleared on flow removal.

This behavior is wrong, causing a leak of resources.
Need to create just one counter per flow, and use it for all sub-flows.

This patch adds the required check to make sure a counter is
created just once per flow, and used by all sub-flows.

Fixes: fa2d01c87d2b ("net/mlx5: support flow aging")
Cc: stable@dpdk.org
Signed-off-by: Dekel Peled <dekelp@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>