sh: Kill off the remaining ST40 cruft.

The ST40 stuff in-tree hasn't built for some time, and hasn't been
updated for over 3 years. ST maintains their own out-of-tree changes
and rebases occasionally, and that's ultimately where all of the ST40
users go anyways.

In order for the ST40 code to be brought up to date most of the stuff
removed in this changeset would have to be rewritten anyways, so there's
very little benefit in keeping the remnants around either.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>