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>