net: rtl8139: Factor out device name assignment

Pull the device name setting into a separate function, as this
will be shared between DM/non-DM variants.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/drivers/net/rtl8139.c b/drivers/net/rtl8139.c
index 0daeefa..cc7fcdf 100644
--- a/drivers/net/rtl8139.c
+++ b/drivers/net/rtl8139.c
@@ -524,6 +524,11 @@
 	return 0;
 }
 
+static void rtl8139_name(char *str, int card_number)
+{
+	sprintf(str, "RTL8139#%u", card_number);
+}
+
 static struct pci_device_id supported[] = {
 	{ PCI_VENDOR_ID_REALTEK, PCI_DEVICE_ID_REALTEK_8139 },
 	{ PCI_VENDOR_ID_DLINK, PCI_DEVICE_ID_DLINK_8139 },
@@ -556,7 +561,7 @@
 		}
 		memset(dev, 0, sizeof(*dev));
 
-		sprintf(dev->name, "RTL8139#%d", card_number);
+		rtl8139_name(dev->name, card_number);
 
 		dev->priv = (void *)devno;
 		dev->iobase = (int)bus_to_phys(iobase);