pci_host: Turn into SysBus-derived QOM type

The preceding commits fixed misuses of FROM_SYSBUS() that led people to
add a bogus busdev field. For qdev the field order was less relevant but
for QOM the PCIHostState field (including the SysBusDevice actually
initialized with a value) must be placed first within the state struct.

To facilitate accessing the PCIHostState fields, derive all PCI host
bridges from TYPE_PCI_HOST_BRIDGE rather than TYPE_SYS_BUS_DEVICE.

We can now access PCIHostState QOM-style, with PCI_HOST_BRIDGE() macro.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
Signed-off-by: NWanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: NAndreas Färber <andreas.faerber@web.de>
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/pci_host.c

@@ -165,4 +165,16 @@ const MemoryRegionOps pci_host_data_be_ops = {
     .endianness = DEVICE_BIG_ENDIAN,
 };
 
+static const TypeInfo pci_host_type_info = {
+    .name = TYPE_PCI_HOST_BRIDGE,
+    .parent = TYPE_SYS_BUS_DEVICE,
+    .abstract = true,
+    .instance_size = sizeof(PCIHostState),
+};
+
+static void pci_host_register_types(void)
+{
+    type_register_static(&pci_host_type_info);
+}
 
+type_init(pci_host_register_types)

hw/pci_host.h

@@ -30,8 +30,13 @@
 
 #include "sysbus.h"
 
+#define TYPE_PCI_HOST_BRIDGE "pci-host-bridge"
+#define PCI_HOST_BRIDGE(obj) \
+    OBJECT_CHECK(PCIHostState, (obj), TYPE_PCI_HOST_BRIDGE)
+
 struct PCIHostState {
     SysBusDevice busdev;
+
     MemoryRegion conf_mem;
     MemoryRegion data_mem;
     MemoryRegion mmcfg;