* Macroize hardware and software descriptor access (much easier to read).
* Simplify and optimize the transmit loop a bit, and use IFF_OACTIVE as
appropriate.
* Fix a potential race condition in the transmit loop. This change has
made the driver significantly more stable (almost completely eliminated
the "device timeout" errors that have plagued this driver).
* Implement transmit interrupt pacing.
* Add missing bus_dmamap_sync() calls (on transmit and receive descriptors
and fraglists). (Draining the write buffer when accessing these structures
may have also contributed to the increased stability of this driver on
the Alpha.)
e8823cc3f3