[coreboot] Tyan s2881 Kconfig

[Myles Watson]

I realize that these boards are old.  If I were new to coreboot and wanted
to experiment with it, I might be looking at boards like this one.  You can
get them for $39 with 2 CPUs (refurbished).

Build tested but not boot tested.

Signed-off-by: Myles Watson

Thanks,
Myles