piix: use TYPE_FOO constants than string constats

Make them more QOMConventional.
Cc:qemu-trivial@nongnu.org
Signed-off-by: NLi Qiang <liq3ea@gmail.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/pci-host/piix.c

@@ -95,6 +95,9 @@ typedef struct PIIX3State {
 #define I440FX_PCI_DEVICE(obj) \
     OBJECT_CHECK(PCII440FXState, (obj), TYPE_I440FX_PCI_DEVICE)
 
+#define TYPE_PIIX3_DEVICE "PIIX3"
+#define TYPE_PIIX3_XEN_DEVICE "PIIX3-xen"
+
 struct PCII440FXState {
     /*< private >*/
     PCIDevice parent_obj;
@@ -424,13 +427,13 @@ PCIBus *i440fx_init(const char *host_type, const char *pci_type,
      * These additional routes can be discovered through ACPI. */
     if (xen_enabled()) {
         PCIDevice *pci_dev = pci_create_simple_multifunction(b,
-                             -1, true, "PIIX3-xen");
+                             -1, true, TYPE_PIIX3_XEN_DEVICE);
         piix3 = PIIX3_PCI_DEVICE(pci_dev);
         pci_bus_irqs(b, xen_piix3_set_irq, xen_pci_slot_get_pirq,
                 piix3, XEN_PIIX_NUM_PIRQS);
     } else {
         PCIDevice *pci_dev = pci_create_simple_multifunction(b,
-                             -1, true, "PIIX3");
+                             -1, true, TYPE_PIIX3_DEVICE);
         piix3 = PIIX3_PCI_DEVICE(pci_dev);
         pci_bus_irqs(b, piix3_set_irq, pci_slot_get_pirq, piix3,
                 PIIX_NUM_PIRQS);
@@ -748,7 +751,7 @@ static void piix3_class_init(ObjectClass *klass, void *data)
 }
 
 static const TypeInfo piix3_info = {
-    .name          = "PIIX3",
+    .name          = TYPE_PIIX3_DEVICE,
     .parent        = TYPE_PIIX3_PCI_DEVICE,
     .class_init    = piix3_class_init,
 };
@@ -761,7 +764,7 @@ static void piix3_xen_class_init(ObjectClass *klass, void *data)
 };
 
 static const TypeInfo piix3_xen_info = {
-    .name          = "PIIX3-xen",
+    .name          = TYPE_PIIX3_XEN_DEVICE,
     .parent        = TYPE_PIIX3_PCI_DEVICE,
     .class_init    = piix3_xen_class_init,
 };