x86/spectre_v2: Don't check bad microcode versions when running under hypervisors.

x86/spectre_v2: Don't check bad microcode versions when running under hypervisors.

As:
 1) We know they lie about the env anyhow (host mismatch)
 2) Even if the hypervisor (Xen, KVM, VMWare, etc) provided
    a valid "correct" value, it all gets to be very murky
    when migration happens (do you provide the "new"
    microcode of the machine?).

And in reality the cloud vendors are the ones that should make
sure that the microcode that is running is correct and we should
just sing lalalala and believe them.

Orabug: 27601736
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>