Fixes for the D-Link DFE-580 card.

This is pretty much fixes any issue I can find:
     -  Watchdog timeouts were due to starting the TX DMA engine
        before we had a packet ready for it.  So the first packet
        sent never got out only if we sent more then one packet
        at a time did the others make it out and not blow up.
        Of course reseting the chip then caused us not to transmit
        the first packet again ie. catch-22.  This required logic changes.
     -  Combine interrupts on TX packets being queued up.
     -  Don't keep running around the RX ring since we might get
        out of sync so only go around once per receive
     -  Let the RX engine recover via the poll interface which is
        similar to the TX interface.  This way the chip wakes
        up with no effort when we read enough packets.
     -  Do better hand-shaking on RX & TX packets so they don't
        start of to soon.
     -  Force a duplex setting when the link comes up after
        an ste_init or it will default to half-duplex and be
        really slow.  This only happens on subsequent ste_init.
        The first one worked.
     -  Don't call stat_update for every overflow.  We only monitor
        the collisions so the tick interval is good enough for that.
        Just read in the collision stats to minimize bus reads.
     -  Don't read the miibus every tick since it uses delays and
        delays are not good for performance.
     -  Tie link events directly to the miibus code so the port
        gets set correctly if someone changes the port settings.
     -  Reduce the extreme number of {R,T}FD's.  They would consume
        130K of kernel memory for each NIC.
     -  Set the TX_THRESH to wait for the DMA engine to complete
        before running the TX FIFO.  This hurts peak TX performance
        but under bi-directional load the DMA engine can't keep up
        with the FIFO.  Testing shows that we end up in the case
        anyways (a la dc(4) issues but worse since the RX engine hogs
	everything).
     -  When stopping the card do a reset since the reset verifies the
	card has stopped.  Otherwise on heavy RX load the RX DMA engine
	is still stuffing packets into memory.  If that happens after
	we free the DMA area memory bits get scribled in memory and
	bad things happen.

This card still has seemingly unfixable issues under heavy RX load in
which the card takes over the PCI bus.

Sponsored by:	Vernier Networks
MFC after:	1 week

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