net/mlx5: change verbs counter allocator to indexed

net/mlx5: change verbs counter allocator to indexed

This is part of the counter optimize which will save the indexed counter
id instead of the counter pointer in the rte_flow.

Place the verbs counter into the container pool helps the counter to be
indexed correctly independent with the raw counter.

The counter pointer in rte_flow will be changed to indexed value after
the DV counter is also changed to indexed.

Signed-off-by: Suanming Mou <suanmingm@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>