pci-assign: Use msi_get_message()

pci-assign only uses a subset of the flexibility msi_get_message()
provides, but it's still worthwhile to use it.
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/kvm/pci-assign.c

@@ -996,12 +996,9 @@ static void assigned_dev_update_msi(PCIDevice *pci_dev)
     }
 
     if (ctrl_byte & PCI_MSI_FLAGS_ENABLE) {
-        uint8_t *pos = pci_dev->config + pci_dev->msi_cap;
-        MSIMessage msg;
+        MSIMessage msg = msi_get_message(pci_dev, 0);
         int virq;
 
-        msg.address = pci_get_long(pos + PCI_MSI_ADDRESS_LO);
-        msg.data = pci_get_word(pos + PCI_MSI_DATA_32);
         virq = kvm_irqchip_add_msi_route(kvm_state, msg);
         if (virq < 0) {
             perror("assigned_dev_update_msi: kvm_irqchip_add_msi_route");