[PATCH] uml: s390 preparation, linkage.h inherited from host

This patch replaces the contents of include/asm-um/linkage.h
by
    #include "asm/arch/linkage.h"

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>