hw: add compat machines for 4.2

Add 4.2 machine types for arm/i440fx/q35/s390x/spapr.

For i440fx and q35, unversioned cpu models are still translated
to -v1, as 0788a56b ("i386: Make unversioned CPU models be
aliases") states this should only transition to the latest cpu
model version in 4.3 (or later).

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20190724103524.20916-1-cohuck@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>