- Fix tx bugs in big-endian machines
    - Remove unused max_interrupt_work module parameter, the new 
      NAPI-like rx scheme doesn't need it.
    - Remove redundancy get_stats() in intr_handler(), those 
      I/O access could affect performance in ARM-based system
    - Add Linux software VLAN support
    - Fix bug of custom mac address 
    (StationAddr register only accept word write)