[TG3]: Fix 5704 single-port mode

If the dual-port 5704 is configured as a single-port device with
only one PCI function, it would trigger a BUG() condition in
tg3_find_5704_peer(). This fixes the problem by returning its
own pdev if the peer cannot be found.
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -10443,8 +10443,13 @@ static struct pci_dev * __devinit tg3_find_5704_peer(struct tg3 *tp)
 			break;
 		pci_dev_put(peer);
 	}
-	if (!peer || peer == tp->pdev)
-		BUG();
+	/* 5704 can be configured in single-port mode, set peer to
+	 * tp->pdev in that case.
+	 */
+	if (!peer) {
+		peer = tp->pdev;
+		return peer;
+	}
 
 	/*
 	 * We don't need to keep the refcount elevated; there's no way