powerpc: Update all configs using savedefconfig

It looks like it's ~4 years since we updated some of these, so do a bulk
update.

Verified that the before and after generated configs are exactly the
same.

Which begs the question why update them? The answer is that it can be
confusing when the stored defconfig drifts too far from the generated
result.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>