[PATCH] solve config broken: undefined reference to `online_page'

Memory hotplug code of i386 adds memory to only highmem.  So, if
CONFIG_HIGHMEM is not set, CONFIG_MEMORY_HOTPLUG shouldn't be set.
Otherwise, it causes compile error.

In addition, many architecture can't use memory hotplug feature yet.  So, I
introduce CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG.

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/Kconfig b/mm/Kconfig
index e76c023..8391729 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -115,7 +115,7 @@
 # eventually, we can have this option just 'select SPARSEMEM'
 config MEMORY_HOTPLUG
 	bool "Allow for memory hot-add"
-	depends on SPARSEMEM && HOTPLUG && !SOFTWARE_SUSPEND
+	depends on SPARSEMEM && HOTPLUG && !SOFTWARE_SUSPEND && ARCH_ENABLE_MEMORY_HOTPLUG
 	depends on (IA64 || X86 || PPC64)
 
 comment "Memory hotplug is currently incompatible with Software Suspend"