[PATCH] add a proper prototype for setup_arch()

This patch adds a proper prototype for setup_arch() in init.h.

This patch is based on a patch by Ben Dooks <ben-linux@fluff.org>.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>