mlxsw: spectrum_matchall: Put matchall list into substruct of flow struct

As there are going to be other matchall specific fields in flow
structure, put the existing list field into matchall substruct.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>