KVM: s390: unintended fallthrough for external call

commit f346026e55f1efd3949a67ddd1dcea7c1b9a615e upstream.

We must not fallthrough if the conditions for external call are not met.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>