KVM: s390: wire up bpb feature

KVM: s390: wire up bpb feature

BugLink: http://bugs.launchpad.net/bugs/1747090
The new firmware interfaces for branch prediction behaviour changes
are transparently available for the guest. Nevertheless, there is
new state attached that should be migrated and properly resetted.
Provide a mechanism for handling reset, migration and VSIE.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
[Changed capability number to 152. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
(back ported from commit 35b3fde6203b932b2b1a5b53b3d8808abc9c4f60)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>