register_memory is global and declared so in linux/memory.h.  Update the
HOTPLUG specific definition to match.  This fixes a compile warning when
HOTPLUG is enabled.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>