fix memory hot remove not configured case.

Now, arch dependent code around CONFIG_MEMORY_HOTREMOVE is a mess.
This patch cleans up them. This is against 2.6.23-rc6-mm1.

 - fix compile failure on ia64/ CONFIG_MEMORY_HOTPLUG && !CONFIG_MEMORY_HOTREMOVE case.
 - For !CONFIG_MEMORY_HOTREMOVE, add generic no-op remove_memory(),
   which returns -EINVAL.
 - removed remove_pages() only used in powerpc.
 - removed no-op remove_memory() in i386, sh, sparc64, x86_64.

 - only powerpc returns -ENOSYS at memory hot remove(no-op). changes it
   to return -EINVAL.

Note:
Currently, only ia64 supports CONFIG_MEMORY_HOTREMOVE. I welcome other
archs if there are requirements and testers.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 947ec0c..3e10152 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c
@@ -718,7 +718,7 @@
 
 	return ret;
 }
-
+#ifdef CONFIG_MEMORY_HOTREMOVE
 int remove_memory(u64 start, u64 size)
 {
 	unsigned long start_pfn, end_pfn;
@@ -734,4 +734,5 @@
 	return ret;
 }
 EXPORT_SYMBOL_GPL(remove_memory);
+#endif /* CONFIG_MEMORY_HOTREMOVE */
 #endif