s390x: Add prefixes to pgm interrupt checks

We need the information about which of the checks failed if there are
more than one and the prefixes provide that.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180919131414.6192-1-frankja@linux.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>