Remove old kernel config fragments and FIT image description

This is like <https://gerrit.chromium.org/gerrit/15233>, but
for the Waluigi kernel.

...actually, though, since Waluigi's kernel is not a cros-workon
project and we didn't need to wait for the PFQ to rev, we could have
done this as part of the last commit that removed the need for
these files <https://gerrit.chromium.org/gerrit/14526>.

BUG=chromium-os:24521
TEST=None

Change-Id: I728f4fb72660062df6714250ec94f0ec5d6401e1
Reviewed-on: https://gerrit.chromium.org/gerrit/15234
Tested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Commit-Ready: Doug Anderson <dianders@chromium.org>
8 files changed