target-i386: kvm: Don't enable MONITOR by default on any CPU model

KVM never supported the MONITOR flag so it doesn't make sense to have it
enabled by default when KVM is enabled.

The rationale here is similar to the cases where it makes sense to have
a feature enabled by default on all CPU models when on KVM mode (e.g.
x2apic). In this case we are having a feature disabled by default for
the same reasons.

In this case we don't need machine-type compat code because it is
currently impossible to run a KVM VM with the MONITOR flag set.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>