KSM will not work on secure pages, because when the kernel reads a
secure page, it will be encrypted and hence no two pages will look the
same.

Let's mark the guest pages as unmergeable when we transition to secure
mode.
Signed-off-by: NJanosch Frank <frankja@linux.ibm.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
[borntraeger@de.ibm.com: patch merging, splitting, fixing]
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>