CRIS: Fix headers_install

Fix headers_install by adjusting the path to arch files.
And delete unused Kbuild file.
Drop special handling of cris in the headers.sh script
as a nice side-effect.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Mikael Starvik <starvik@axis.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>