net/mlx5e: Force CHECKSUM_UNNECESSARY for short ethernet frames for 4.19.17

Hey,

This issue on 4.19 makes us sad:

* https://bugzilla.kernel.org/show_bug.cgi?id=201849 * https://www.mail-archive.com/netdev@vger.kernel.org/msg253346.html

Luckily, fix for this landed in v5.0-rc3:

* https://patchwork.ozlabs.org/patch/1027838/

It doesn't apply cleanly on v4.19.16, so I made a backported version:

* https://github.com/bobrik/linux/commit/1c7cbb3cb62cf

This fixed the issue for us and we'd like to have the fix included in v4.19.17 in some way. There are four patches in the series applied to v5.0-rc3, I'm not sure if others need to be backported as well.

Thanks!