x86: remove support for the Rise CPU

The Rise CPUs were only very short-lived, and there are no reports of
anyone both owning one and running Linux on it.

Googling for the printk string "CPU: Rise iDragon" didn't find any dmesg
available online.

If it turns out that against all expectations there are actually users
reverting this patch would be easy.

This patch will make the kernel images smaller by a few bytes for all
i386 users.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>