[PATCH] mm/page_alloc: use NULL instead of 0 for ptr

Use NULL instead of 0 for pointer value, eliminate sparse warnings.
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/page_alloc.c

@@ -1591,7 +1591,7 @@ static int __meminit __build_all_zonelists(void *dummy)
 void __meminit build_all_zonelists(void)
 {
 	if (system_state == SYSTEM_BOOTING) {
-		__build_all_zonelists(0);
+		__build_all_zonelists(NULL);
 		cpuset_init_current_mems_allowed();
 	} else {
 		/* we have to stop all cpus to guaranntee there is no user