vlan: updates vlan real_num_tx_queues

Updates real_num_tx_queues in case underlying real device
has changed real_num_tx_queues.

-v2
 As per Eric Dumazet<eric.dumazet@gmail.com> comment:-
   -- adds BUG_ON to catch case of real_num_tx_queues exceeding num_tx_queues.
   -- created this self contained patch to just update real_num_tx_queues.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan.c

@@ -378,6 +378,8 @@ static void vlan_transfer_features(struct net_device *dev,
 #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
 	vlandev->fcoe_ddp_xid = dev->fcoe_ddp_xid;
 #endif
+	vlandev->real_num_tx_queues = dev->real_num_tx_queues;
+	BUG_ON(vlandev->real_num_tx_queues > vlandev->num_tx_queues);
 
 	if (old_features != vlandev->features)
 		netdev_features_change(vlandev);