Since the flex keys for Spectrum-2 differ not only in blocks definitions
but also in encoding layout, prepare for the implementation and pass
Spectrum/Spectrum-2 specific ops down to mlxsw_afk_create.

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>