mlx4: Fix vlan table overflow

mlx4: Fix vlan table overflow

commit e72ebf5a578464204c8418d7d9b375333bb33161
Author: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Date:   Tue Oct 18 01:50:29 2011 +0000

    mlx4: Fix vlan table overflow

    Prevent overflow when trying to register more Vlans then the Vlan table in
    HW is configured to.
    Need to take into acount that the first 2 entries are reserved.

    Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Joe Jin <joe.jin@oracle.com>