myri_sbus: remove driver

Remove the myri_sbus driver. Why?
* There is no possibility of ethernet mode on this adapter, so it's
  Myrinet only.
* It won't inter-op with modern versions of Myrinet, and thus can only
  work with legacy adapters.
* There are no in-kernel Linux drivers for the PCI version of this
  adapter, so it only can work on ~15 year old Sun hardware.

It's long in the tooth, let's take it to the knackers.

Signed-off-by: Jon Mason <mason@myri.com>
Signed-off-by: David S. Miller <davem@davemloft.net>