switch back to MII mode. Keep a sliding window for TX segments and when it
gets > 2/3 full, request a TX interrupt (window gets reset when the h/w TX
queue is empty). Add dv_xname to a few printfs. With the above changes,
the gem driver will now work on Macintoshes, even in GigE mode. On a 733
PowerMac G4 it gets ~355Mb/s TX and ~280Mb/s RX to/from an Alpha XP1000.
XXX mii autoselect is still flakey.
gem_mediachange(). This will cause gem_mii_statchg() to be called
by the MII layer with the correct MII media state, so that speed
duplex parameters will be set properly.
