hw/s390x: add SCLP event type CPI

hw/s390x: add SCLP event type CPI

Implement the Service-Call Logical Processor (SCLP) event
type Control-Program Identification (CPI) in QEMU. This
event is used to send CPI identifiers from the guest to the
host. The CPI identifiers are: system type, system name,
system level and sysplex name.

System type: operating system of the guest (e.g. "LINUX   ").
System name: user configurable name of the guest (e.g. "TESTVM  ").
System level: distribution and kernel version, if the system type is Linux
(e.g. 74872343805430528).
Sysplex name: name of the cluster which the guest belongs to (if any)
(e.g. "PLEX").

The SCLP event CPI is supported only from "s390-ccw-virtio-10.1" machine
and higher.

Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250616140107.990538-2-shalini@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>