paravirt: add a hook for once the allocator is ready

Add a hook so that the paravirt backend knows when the allocator is
ready.  This is useful for the obvious reason that the allocator is
available, but the other side-effect of having the bootmem allocator
available is that each page now has an associated "struct page".

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
diff --git a/include/asm-i386/setup.h b/include/asm-i386/setup.h
index 0d5bff9..7862fe8 100644
--- a/include/asm-i386/setup.h
+++ b/include/asm-i386/setup.h
@@ -81,6 +81,10 @@
 
 extern unsigned long init_pg_tables_end;
 
+#ifndef CONFIG_PARAVIRT
+#define paravirt_post_allocator_init()	do {} while (0)
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif  /*  __KERNEL__  */