target/s390x: Remove duplicated ifdef macro

target/s390x: Remove duplicated ifdef macro

Commit ae71ed8610 replaced the use of global max_cpus variable
with a machine property, but introduced a unnecessary ifdef, as
this block is already in the 'not CONFIG_USER_ONLY' branch part:

   86 #if defined(CONFIG_USER_ONLY)
   87
  ...
  106 #else /* !CONFIG_USER_ONLY */
  107
  ...
  292 static void do_ext_interrupt(CPUS390XState *env)
  293 {
  ...
  313 #ifndef CONFIG_USER_ONLY
  314         MachineState *ms = MACHINE(qdev_get_machine());
  315         unsigned int max_cpus = ms->smp.max_cpus;
  316 #endif

To ease code review, remove the duplicated preprocessor macro,
and move the declarations at the beginning of the statement.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200121110349.25842-6-philmd@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>