RDMA/mlx5: Enable attaching packet reformat action to steering flows

Any matching rules will be mutated based on the packet reformat context
which is attached to that given flow rule.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>