mlxsw: spectrum: Add Spectrum-2 variant of flex actions ops

In Spectrum-2, no action set is stored directly in TCAM, all are located
in KVD linear. So ask core to treat the first set as dummy empty one,
to be just used for PTCEV2 purposes.

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>