UAPI: Fix up empty files in arch/cris/

Fix up three empty files in arch/cris/ by sticking placeholder comments in
there to prevent the patch program from deleting them.

I decided not to delete the arch-v*/Kbuild files as it's possibly someone might
want to use them for genhdr-y lines in the future, but they could be deleted
and the pointer lines removed from asm/Kbuild.  The uapi/arch-v*/Kbuild files
ought to be uneffected by such a change.

asm/swab.h didn't have anything outside of __KERNEL__ so nothing appeared in
uapi/asm/swab.h.  The latter, however, is exported by Kbuild.asm.

This needs to be applied after the CRIS UAPI disintegration patch.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NJesper Nilsson <jesper.nilsson@axis.com>

arch/cris/include/arch-v10/arch/Kbuild

+# CRISv10 arch

arch/cris/include/arch-v32/arch/Kbuild

+# CRISv32 arch

arch/cris/include/uapi/asm/swab.h

+/*
+ * CRIS byte swapping.
+ */