Add 7.2 machine types for arm/i440fx/m68k/q35/s390x/spapr.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220727121755.395894-1-cohuck@redhat.com>
[thuth: fixed conflict with pcmc->legacy_no_rng_seed]
Signed-off-by: Thomas Huth <thuth@redhat.com>