The commit 
e2c0388866dc12bef56b178b958f9b778fe6c687 added
setup_additional_cpus to setup.c but this is only defined if
CONFIG_HOTPLUG_CPU is set.  This patch changes the #ifdef to reflect that.
Signed-off-by: Brian Magnuson <magnuson@rcn.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
                        elfcorehdr_addr = memparse(from+11, &from);
 #endif
 
-#ifdef CONFIG_SMP
+#ifdef CONFIG_HOTPLUG_CPU
                else if (!memcmp(from, "additional_cpus=", 16))
                        setup_additional_cpus(from+16);
 #endif