net/mlx5e: Introduce timestamps statistic counter for Tx DMA layer

Count number of transmitted packets that were hardware timestamped at the
device DMA layer.

Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Link: https://lore.kernel.org/r/20240403212931.128541-4-rrameshbabu@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>