[S390] guest page hinting light

Use the existing arch_alloc_page/arch_free_page callbacks to do
the guest page state transitions between stable and unused.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/include/asm-s390/system.h b/include/asm-s390/system.h
index c819ae2..e0d4500 100644
--- a/include/asm-s390/system.h
+++ b/include/asm-s390/system.h
@@ -116,6 +116,12 @@
 #define pfault_fini()		do { } while (0)
 #endif /* CONFIG_PFAULT */
 
+#ifdef CONFIG_PAGE_STATES
+extern void cmma_init(void);
+#else
+static inline void cmma_init(void) { }
+#endif
+
 #define finish_arch_switch(prev) do {					     \
 	set_fs(current->thread.mm_segment);				     \
 	account_vtime(prev);						     \