net/mlx5: DR, Modify header action of size 1 optimization

Set modify header action of size 1 directly on the STE for supporting
devices, thus reducing number of hops and cache misses.

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>