kprobes: fix sparse NULL warning

Fix sparse NULL warnings:
kernel/kprobes.c:915:49: warning: Using plain integer as NULL pointer
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kprobes.c

@@ -35,6 +35,7 @@
 #include <linux/hash.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/stddef.h>
 #include <linux/module.h>
 #include <linux/moduleloader.h>
 #include <linux/kallsyms.h>
@@ -912,7 +913,7 @@ static int __kprobes debugfs_kprobe_init(void)
 	if (!dir)
 		return -ENOMEM;
 
-	file = debugfs_create_file("list", 0444, dir , 0 ,
+	file = debugfs_create_file("list", 0444, dir, NULL,
 				&debugfs_kprobes_operations);
 	if (!file) {
 		debugfs_remove(dir);