CRIS: Drop support for the CRIS port

The port was added back in 2000 so it's no longer even a good source
of inspiration for newer ports (if it ever was)

The last SoC (ARTPEC-3) with a CRIS main CPU was launched in 2008.

Coupled with time and working developer board hardware being
in low supply, it's time to drop the port from Linux.

So long and thanks for all the fish!

Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>