pc, pc_piix: split out pc nic initialization

Factor out pc nic initialization.
This simplifies the pc initialization and will reduce the code
duplication of q35 pc initialization.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/pc.h b/hw/pc.h
index e7993ca..d6639a6 100644
--- a/hw/pc.h
+++ b/hw/pc.h
@@ -98,6 +98,7 @@
                   const char *boot_device,
                   ISADevice *floppy, BusState *ide0, BusState *ide1,
                   ISADevice *s);
+void pc_nic_init(ISABus *isa_bus, PCIBus *pci_bus);
 void pc_pci_device_init(PCIBus *pci_bus);
 
 typedef void (*cpu_set_smm_t)(int smm, void *arg);