Remove duplicate listing of Cris arch from README

Mikael Pettersson pointed out to me that a recent patch of mine (commit
620034c8

), that made some corrections to the
README file, accidentally listed the Cris architecture twice.  Whoops.

This patch removes the duplicate.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>