s390x/cpumodel: ignore csske for expansion

csske will be removed in a future machine. Ignore it for expanding the
cpu model. Otherwise qemu falls back to z9.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20190429090250.7648-3-borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
(cherry picked from commit eaf6f64)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

target/s390x/cpu_models.c

@@ -1297,6 +1297,8 @@ static void init_ignored_base_feat(void)
          S390_FEAT_KM_TDEA_192,
          S390_FEAT_KIMD_SHA_1,
          S390_FEAT_KLMD_SHA_1,
+         /* CSSKE is deprecated on newer generations */
+         S390_FEAT_CONDITIONAL_SSKE,
     };
     int i;