KVM: s390: Add a routine for setting userspace CPU state

KVM: s390: Add a routine for setting userspace CPU state

This capability exists, but we don't record anything when userspace
enables it. Let's refactor that code so that a note can be made in
the debug logs that it was enabled.

Signed-off-by: Eric Farman <[email protected]>
Reviewed-by: Thomas Huth <[email protected]>
Reviewed-by: Claudio Imbrenda <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Borntraeger <[email protected]>