s390x/pci: don't fence interpreted devices without MSI-X

s390x/pci: don't fence interpreted devices without MSI-X

Lack of MSI-X support is not an issue for interpreted passthrough
devices, so let's let these in.  This will allow, for example, ISM
devices to be passed through -- but only when interpretation is
available and being used.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20220902172737.170349-5-mjrosato@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>