Implemented from the Linux driver:

Implemented from the Linux driver:

* Introduce split transaction order queues.
* Improve the NAK interrupt handler routine.
* Mostly move from list_move() to list_move_tail().

Those changes fix an attachment problem seen for certain devices which
are issuing NAK interrupts during split transactions, which don't get
handled correctly by the driver today.  This could result in unexpected
channel halting, printing "ChHltd set, but reason is unknown", which
finally leaves the device back on a disabled USB port.

ok kettenis@