net/mlx5: fix MPRQ WQE size assertion

net/mlx5: fix MPRQ WQE size assertion

Preparation of the stride size and the number of strides for
Multi-Packet RQ was updated recently to accommodate the hardware
limitation about minimum WQE size. The wrong assertion was
introduced to ensure this limitation is met. Assert that the
configured WQE size is not less than the minimum supported size.

Fixes: 34776af600df ("net/mlx5: fix MPRQ stride devargs adjustment")
Cc: stable@dpdk.org
Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>