bonding: clean up bond_del_vlan()

1) the setting of NETIF_F_VLAN_CHALLENGED in bond_del_vlan() is
useless since commit b2a103e6 because bond_fix_features() now
sets NETIF_F_VLAN_CHALLENGED whenever the last slave is being
removed.

2) the code never triggers anyway as vlan_list is never empty
since ad1afb00.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -329,16 +329,6 @@ static int bond_del_vlan(struct bonding *bond, unsigned short vlan_id)
 
 			kfree(vlan);
 
-			if (list_empty(&bond->vlan_list) &&
-			    (bond->slave_cnt == 0)) {
-				/* Last VLAN removed and no slaves, so
-				 * restore block on adding VLANs. This will
-				 * be removed once new slaves that are not
-				 * VLAN challenged will be added.
-				 */
-				bond->dev->features |= NETIF_F_VLAN_CHALLENGED;
-			}
-
 			res = 0;
 			goto out;
 		}