Support for the new 2940U2W

[Justin T. Gibbs]

>Ohhh, great.  Don't tell me they did like they did with the 7895 and just
>made some registers "go away"

The main change to deal with is that the sync period and offset are 
separated into two registers.  They did this since the chip can handle
an offset count of 127 now.  They also added a few other nifty things
I'd like to support such as the bus utilization counters, a special
register that you can use to send messages to the sequencer without
pausing it, and the extra DMA fifo that the 7895 also has.

>Now, I know why they want LVD for Ultra2 speeds (it's more reliable and
>robust in how it does the signalling, just like differential is now, for
>instance, it can handle longer cable lengths and what not, plus with the
>lower voltage there is less signal noise generated, etc), what I don't know
>is if someone writing their own sequencer can "cheat" on this and still run
>an Ultra2 device at Ultra2 speeds regardless of the bus type in use.

My guess is that an LVD drive on an SE bus will not allow sync rates over
20MHz, so the driver's behavior is moot.

--
Justin