KVM: s390: protvirt: Add program exception injection

Only two program exceptions can be injected for a protected guest:
specification and operand.

For both, a code needs to be specified in the interrupt injection
control of the state description, as the guest prefix page is not
accessible to KVM for such guests.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
[borntraeger@de.ibm.com: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>