s390/PCI: Fix single MSI only check

Multiple MSIs have never been supported on s390 architecture, but the
platform code fails to report single MSI only.
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/pci/pci.c

@@ -409,6 +409,8 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
 
 	if (type != PCI_CAP_ID_MSIX && type != PCI_CAP_ID_MSI)
 		return -EINVAL;
+	if (type == PCI_CAP_ID_MSI && nvec > 1)
+		return 1;
 	msi_vecs = min(nvec, ZPCI_MSI_VEC_MAX);
 	msi_vecs = min_t(unsigned int, msi_vecs, CONFIG_PCI_NR_MSI);