s390x/smp: add minimal test for sigp sense running status

Two minimal tests:
- our own CPU should be running when we check ourselves
- a CPU should at least have some times with a not running
indication. To speed things up we stop CPU1

Also rename smp_cpu_running to smp_sense_running_status.

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20200402154441.13063-1-borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>