ARM: orion: remove unused board files

As planned earlier, all board support that was marked unused can be
removed now after nobody explicitly asked for these to be kept.

In particular, all of the reference designs get removed now, as these
are not commonly used productively any more. Also, the machines that
were not supported by Debian or the Debian_on_Buffalo group because of
limitations with RAM size are gone.

Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>