target/s390x: Use start-powered-off CPUState property

Instead of setting CPUState::halted to 1 in s390_cpu_initfn(), use the
start-powered-off property which makes cpu_common_reset() initialize it
to 1 in common code.

Note that this changes behavior by setting cs->halted to 1 on reset, which
didn't happen before.

Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Message-Id: <20200826055535.951207-9-bauerman@linux.ibm.com>
[dwg: Fix from Laurent Vivier for user only case]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

target/s390x/cpu.c

@@ -291,9 +291,9 @@ static void s390_cpu_initfn(Object *obj)
     S390CPU *cpu = S390_CPU(obj);
 
     cpu_set_cpustate_pointers(cpu);
-    cs->halted = 1;
     cs->exception_index = EXCP_HLT;
 #if !defined(CONFIG_USER_ONLY)
+    cs->start_powered_off = true;
     object_property_add(obj, "crash-information", "GuestPanicInformation",
                         s390_cpu_get_crash_info_qom, NULL, NULL, NULL);
     cpu->env.tod_timer =