net/mlx5: update modify header action translator

net/mlx5: update modify header action translator

When composing device command for modify header action, provided mask
should be taken more accurate into account thus length and offset
in action should be set accordingly at precise bit-wise boundaries.

For the future use, metadata register copy action is also added.

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>