mlxsw: spectrum_acl: Push rehash dw struct into rehash sub-struct

More rehash related fields are going to come. Push "dw" into sub-struct
that will accommodate the others as well.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>