s390x: smp: Use full PSW to bringup new cpu

Up to now we ignored the psw mask and only used the psw address when
bringing up a new cpu. For DAT we need to also load the mask, so let's
do that.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20200429143518.1360468-8-frankja@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>