s390x: introduce and use S390_MAX_CPUS

Will be handy in the future.
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20170928134609.16985-6-david@redhat.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

hw/s390x/s390-virtio-ccw.c

@@ -423,7 +423,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void *data)
     mc->no_parallel = 1;
     mc->no_sdcard = 1;
     mc->use_sclp = 1;
-    mc->max_cpus = 248;
+    mc->max_cpus = S390_MAX_CPUS;
     mc->has_hotpluggable_cpus = true;
     mc->get_hotplug_handler = s390_get_hotplug_handler;
     mc->cpu_index_to_instance_props = s390_cpu_index_to_props;

target/s390x/cpu.h

@@ -60,6 +60,8 @@
 #define PSW_MCHK_MASK 0x0004000000000000
 #define PSW_IO_MASK 0x0200000000000000
 
+#define S390_MAX_CPUS 248
+
 typedef struct PSW {
     uint64_t mask;
     uint64_t addr;