net/mlx5: Add copy header action struct layout

Add definition for copy header action, copy action is used
to copy header fields from source to destination.

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