virtio bus: Fix resource leak. CID 1032283

* bus is allocated but not deleted and not used
  after an error

src/add-ons/kernel/busses/virtio/virtio_pci.cpp

@@ -252,7 +252,6 @@ init_bus(device_node* node, void** bus_cookie)
 
 	pci_device_module_info* pci;
 	pci_device* device;
-		
 	{
 		device_node* parent = gDeviceManager->get_parent_node(node);
 		device_node* pciParent = gDeviceManager->get_parent_node(parent);
@@ -276,6 +275,7 @@ init_bus(device_node* node, void** bus_cookie)
 	bus->irq = pciInfo.u.h0.interrupt_line;
 	if (bus->irq == 0 || bus->irq == 0xff) {
 		ERROR("PCI IRQ not assigned\n");
+		delete bus;
 		return B_ERROR;
 	}