config: Eliminate unused ppc/ppc64 configs.
The history of the ppc/ppc64 configs is a convoluted one that started
before the kernel source could support multiple machine types with a
single image and before there was a usable 64-bit userspace.
In the subsequent years, the powerpc code has been unified and we've
released a 64-bit powerpc userspace. The "default" and "ppc64" configs
on ppc64 are essentially identical and just waste space. The "ppc64"
config on 32-bit ppc address a long since unnecessary corner case. Users
who still want a 32-bit userspace with a 64-bit kernel can install and
update it themselves using the 64-bit repository like i386/x86_64 users
can do.
This commit can be summarized thusly:
rm config/ppc/ppc64
rm config/ppc/ps3 (already unused)
mv config/ppc64/ppc64 config/ppc64/default