net/mlx5e: Add hds-thresh query support via ethtool

net/mlx5e: Add hds-thresh query support via ethtool

Add support for reporting HDS (Header-Data Split) threshold via
ethtool. When applicable, mlx5 hardware splits packets of all sizes with
no configurable threshold, so report both hds-thresh and hds-thresh-max
as 0 (i.e. always split regardless of size).

Signed-off-by: Nimrod Oren <noren@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260317104934.16124-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>