net/mlx5: fix Rx queue completion index consistency

net/mlx5: fix Rx queue completion index consistency

The Rx queue completion consumer index got temporary
wrong value pointing to the midst of the compressed CQE
session. If application crashed at the moment the next
queue restart caused handling wrong CQEs pointed by index
and losing consuming index synchronization, that made
reliable queue restart impossible.

Fixes: 88c0733535d6 ("net/mlx5: extend Rx completion with error handling")
Cc: stable@dpdk.org
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>