Reduce brokenness of CRIS headers_install

I won't say 'fix', because they still look broken, although this will at
least allow 'make ARCH=CRIS headers_install' to _complete_.

For headers which are exported, we should probably choose between
asm/arch-v10 and asm/arch-v32 by something that GCC defines -- we can't
rely on a generated symlink. And we certainly can't export an arch/
directory which doesn't even exist.

And the only thing that we seem to include from the arch/ directory is
<asm/arch/ptrace.h> from <asm/ptrace.h> ... and that isn't exported in
either arch-v10 or arch-v32 _anyway_.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>