KVM: s390: Enable the KVM-VFIO device

The KVM-VFIO device is used by the QEMU VFIO device. It is used to
record the list of in-use VFIO groups so that KVM can manipulate
them.
While we don't need this on s390 currently, let's try to be like
everyone else.

Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/Kconfig

@@ -29,6 +29,7 @@ config KVM
 	select HAVE_KVM_IRQFD
 	select HAVE_KVM_IRQ_ROUTING
 	select SRCU
+	select KVM_VFIO
 	---help---
 	  Support hosting paravirtualized guest machines using the SIE
 	  virtualization capability on the mainframe. This should work