[PATCH v3] doc: add mlx5 PMD flex item documentation

[Ferruh Yigit]

On 11/23/2021 9:29 AM, Gregory Etelson wrote:
> Describe firmware configuration requirements.
> List mlx5 hardware and PMD limitations.
> 
> Signed-off-by: Gregory Etelson <getelson at nvidia.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
> Acked-by: Raslan Darawsheh <rasland at nvidia.com>
> ---
> v2: Style fixes.
> v3: Update hardware and port support.

Patch is already in next-net-mlx tree, pulled from there to next-net.