kernel: fix integer as NULL pointer warnings

kernel/cpuset.c:1268:52: warning: Using plain integer as NULL pointer
kernel/pid_namespace.c:95:24: warning: Using plain integer as NULL pointer

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Reviewed-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 6d792b6..5ca37fa 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -92,7 +92,7 @@
 	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
 
 	for (i = 1; i < PIDMAP_ENTRIES; i++) {
-		ns->pidmap[i].page = 0;
+		ns->pidmap[i].page = NULL;
 		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
 	}