Set Link State from VBox to 86Box implemented on the PCnet card (any other nics don't have it and will simply return NULL).

The PCnet-based Racal nic now has its own OID to make its drivers happy (according to VBox).

src/network/net_3c503.c

@@ -617,7 +617,7 @@ threec503_nic_init(const device_t *info)
     dev->regs.gacfr = 0x09;	/* Start with RAM mapping enabled. */
 
     /* Attach ourselves to the network module. */
-    network_attach(dev->dp8390, dev->dp8390->physaddr, dp8390_rx, NULL);
+    network_attach(dev->dp8390, dev->dp8390->physaddr, dp8390_rx, NULL, NULL);
 
     return(dev);
 }