target/s390x: Have s390_cpu_halt() not return anything

Since halting a vCPU and how many left running do not need
to be tied together, split the s390_count_running_cpus()
call out of s390_cpu_halt() to the single caller using it:
s390_handle_wait().

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250708095746.12697-4-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
3 files changed