xen: fix 2.6.27-rc5 xen balloon driver warnings

Set the class so it doesn't clash with the normal memory class.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
===================================================================

drivers/xen/balloon.c

@@ -60,7 +60,7 @@
 
 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
 
-#define BALLOON_CLASS_NAME "memory"
+#define BALLOON_CLASS_NAME "xen_memory"
 
 struct balloon_stats {
 	/* We aim for 'current allocation' == 'target allocation'. */