Add a definition for cpu_show_spectre_v2() to override the generic
version. This has several permuations, though in practice some may not
occur we cater for any combination.
We don't treat the ori31 speculation barrier as a mitigation on its
own, because it has to be *used* by code in order to be a mitigation
and we don't know if userspace is doing that. So if that's all we see
we say:
Vulnerable, ori31 speculation barrier enabled
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>