s390x: css: implementing Set CHannel Monitor

We implement the call of the Set CHannel Monitor instruction,
starting the monitoring of the all Channel Sub System, and
initializing channel subsystem monitoring.

Initial tests report the presence of the extended measurement block
feature, and verify the error reporting of the hypervisor for SCHM.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/kvm/1615545714-13747-5-git-send-email-pmorel@linux.ibm.com/


Signed-off-by: Janosch Frank <frankja@linux.ibm.com>