Add support for dual network (net_device) interface so that ethernet
and wireless can own separate ethX interfaces.

V2
  - Fix the bug that bringing down and up the interface keeps rx
    disabled.
  - Make 'gelic_net_poll_controller()' extern , as David Woodhouse
    pointed out at the previous submission.
  - Fix weird usage of member names for the rx descriptor chain
V1
  - Export functions which are convenient for both interfaces
  - Move irq allocation/release code to driver probe/remove handlers
    because interfaces share interrupts.
  - Allocate skbs by using dev_alloc_skb() instead of netdev_alloc_skb()
    as the interfaces share the hardware rx queue.
  - Add gelic_port struct in order to abstract dual interface handling
  - Change handlers for hardware queues so that they can handle dual
    {source,destination} interfaces.
  - Use new NAPI functions
This is a prerequisite for the new PS3 wireless support.
Signed-off-by: Jeff Garzik <jeff@garzik.org>