forcedeth: call vlan_mode only if hw supports vlans

If hw does not support vlans, dont call nv_vlan_mode because it has no point.
I believe that this should fix issues on older non-vlan supportive
chips (like Ingo has).

Reported-ty: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/forcedeth.c b/drivers/net/forcedeth.c
index e55df30..6d5fbd4 100644
--- a/drivers/net/forcedeth.c
+++ b/drivers/net/forcedeth.c
@@ -5615,7 +5615,8 @@
 		goto out_error;
 	}
 
-	nv_vlan_mode(dev, dev->features);
+	if (id->driver_data & DEV_HAS_VLAN)
+		nv_vlan_mode(dev, dev->features);
 
 	netif_carrier_off(dev);