hw/net/lasi_i82596: use qemu_create_nic_device()

Create the device only if there is a corresponding NIC config for it.
Remove the explicit check on nd_table[0].used from hw/hppa/machine.c
which (since commit d8a3220005) tries to do the same thing.

The lasi_82596 support has been disabled since it was first introduced,
since enable_lasi_lan() has always been zero. This allows the user to
enable it by explicitly requesting a NIC model 'lasi_82596' or just
using the alias 'lasi'. Otherwise, it defaults to a PCI NIC as before.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>

hw/hppa/machine.c

@@ -362,14 +362,13 @@ static void machine_HP_common_init_tail(MachineState *machine, PCIBus *pci_bus,
     }
 
     /* Network setup. */
-    if (nd_table[0].used && enable_lasi_lan()) {
+    if (lasi_dev) {
         lasi_82596_init(addr_space, translate(NULL, LASI_LAN_HPA),
-                        qdev_get_gpio_in(lasi_dev, LASI_IRQ_LAN_HPA));
+                        qdev_get_gpio_in(lasi_dev, LASI_IRQ_LAN_HPA),
+                        enable_lasi_lan());
     }
 
-    if (!enable_lasi_lan()) {
-        pci_init_nic_devices(pci_bus, mc->default_nic);
-    }
+    pci_init_nic_devices(pci_bus, mc->default_nic);
 
     /* BMC board: HP Powerbar SP2 Diva (with console only) */
     pci_dev = pci_new(-1, "pci-serial");