tg3: Refine tg3_vlan_rx_register()

tg3_vlan_rx_register() touches the hardware if netif_running() returns
false.  This patch fixes the problem.
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -9896,8 +9896,12 @@ static void tg3_vlan_rx_register(struct net_device *dev, struct vlan_group *grp)
 {
 	struct tg3 *tp = netdev_priv(dev);
 
-	if (netif_running(dev))
-		tg3_netif_stop(tp);
+	if (!netif_running(dev)) {
+		tp->vlgrp = grp;
+		return;
+	}
+
+	tg3_netif_stop(tp);
 
 	tg3_full_lock(tp, 0);
 
@@ -9906,8 +9910,7 @@ static void tg3_vlan_rx_register(struct net_device *dev, struct vlan_group *grp)
 	/* Update RX_MODE_KEEP_VLAN_TAG bit in RX_MODE register. */
 	__tg3_set_rx_mode(dev);
 
-	if (netif_running(dev))
-		tg3_netif_start(tp);
+	tg3_netif_start(tp);
 
 	tg3_full_unlock(tp);
 }