net/mlx5: DR, Modify header copy support

Modify header supports ADD/SET and from this patch
also COPY. Copy allows to copy header fields and
metadata.

Signed-off-by: Hamdan Igbaria <hamdani@mellanox.com>
Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>