[PATCH] fix build of ibmstb4 and ibmstbx25

Hi Tom,

config.in.diff adds two missing '$' for config variables in
arch/ppc/config.in and the two other patches update the ocp definitions
for the stb4xxx and stbx25xx CPUs, so they can be built again. I used
linuxppc_2_4_devel, but they are needed for linuxppc-2.4, too.

Any idea why my changes to config.in were visible with bk difftool but
not with bk diffs? It's the first time I tried to use bk for creating
patches and I really don't like it. :)

Regards,
Andreas