iommu/s390: Fail probe for non-PCI devices

s390-iommu only supports pci_bus_type today.
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/8cb71ea1b24bd2622c1937bd9cfffe73b126eb56.1660572783.git.robin.murphy@arm.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/s390-iommu.c

@@ -185,7 +185,12 @@ static void s390_iommu_detach_device(struct iommu_domain *domain,
 
 static struct iommu_device *s390_iommu_probe_device(struct device *dev)
 {
-	struct zpci_dev *zdev = to_zpci_dev(dev);
+	struct zpci_dev *zdev;
+
+	if (!dev_is_pci(dev))
+		return ERR_PTR(-ENODEV);
+
+	zdev = to_zpci_dev(dev);
 
 	return &zdev->iommu_dev;
 }