Make PCI bus initialization code more generic

Register PCI bus to io_bus at x86-64 architecutre specific code.

src/arch/x86/vm.c

@@ -117,7 +117,9 @@ int vm_arch_cpu_init(vm_t *v)
 
 int vm_arch_init_platform_device(vm_t *v)
 {
-    pci_init(&v->pci, &v->io_bus);
+    pci_init(&v->pci);
+    bus_register_dev(&v->io_bus, &v->pci.pci_addr_dev);
+    bus_register_dev(&v->io_bus, &v->pci.pci_bus_dev);
     if (serial_init(&v->serial, &v->io_bus))
         return throw_err("Failed to init UART device");
     virtio_blk_init(&v->virtio_blk_dev);

src/pci.c

@@ -173,13 +173,11 @@ void pci_dev_register(struct pci_dev *dev)
 #define PCI_CONFIG_ADDR 0xCF8
 #define PCI_CONFIG_DATA 0xCFC
 
-void pci_init(struct pci *pci, struct bus *io_bus)
+void pci_init(struct pci *pci)
 {
     dev_init(&pci->pci_addr_dev, PCI_CONFIG_ADDR, sizeof(uint32_t), pci,
              pci_address_io);
     dev_init(&pci->pci_bus_dev, PCI_CONFIG_DATA, sizeof(uint32_t), pci,
              pci_data_io);
     bus_init(&pci->pci_bus);
-    bus_register_dev(io_bus, &pci->pci_addr_dev);
-    bus_register_dev(io_bus, &pci->pci_bus_dev);
 }

src/pci.h

@@ -55,4 +55,4 @@ void pci_dev_init(struct pci_dev *dev,
                   struct pci *pci,
                   struct bus *io_bus,
                   struct bus *mmio_bus);
-void pci_init();
+void pci_init(struct pci *pci);