[CFT] forcedeth backport to 2.4

[Manfred Spraul]

Hi,

Attached is a backport of the latest forcedeth version to 2.4. It
includes lots of changes, among them:
- a critical bugfix for nv_open(): ifdown/ifup cycles resulted in an
incomplete initialization that causes hangs after a few MB network traffic.
- jumbo frame support
- far better ethtool support
- 64-bit dma support
- support for additional nforce versions.

It compiles and boots, but I can't test it properly. Could you give it a
try?

--
Manfred