[S390] disable MACHINE_IS_VM check for pfault

This patch disables the check for MACHINE_IS_VM when initializing the
pfault infrastructure. The code checks for successful completion of
diag 258 anyway, thus it's safe to try initialization on LPAR anyway.
This is needed to use pfault on kvm

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>