docs/s390x/cpu topology: document s390x cpu topology

Add some basic examples for the definition of cpu topology
in s390x.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Message-ID: <20231016183925.2384704-15-nsg@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>