compress/mlx5: fix compression level translation

compress/mlx5: fix compression level translation

Compression Level is interpreted by each PMD differently.
However, lower numbers give faster compression
at the expense of compression ratio, while higher numbers
may give better compression ratios but are likely slower.
The level affects the block size, which affects performance,
the bigger the block, the faster the compression is.

The problem was that higher levels caused bigger blocks:
  size = min_block_size - 1 + level.

the solution is to reverse the above:
  size = max_block_size + 1 - level.

Fixes: 39a2c8715f8f ("compress/mlx5: add transformation operations")
Cc: stable@dpdk.org
Signed-off-by: Raja Zidane <rzidane@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>