staging:lustre: Fix sparse warning of plain integer as NULL

This patch fixes the following sparse warning:
drivers/staging/lustre/lustre/lov/lov_request.c:53:28: warning: Using plain integer as NULL pointer

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>

drivers/staging/lustre/lustre/lov/lov_request.c

@@ -50,7 +50,7 @@ static void lov_init_set(struct lov_request_set *set)
 	atomic_set(&set->set_completes, 0);
 	atomic_set(&set->set_success, 0);
 	atomic_set(&set->set_finish_checked, 0);
-	set->set_cookies = 0;
+	set->set_cookies = NULL;
 	INIT_LIST_HEAD(&set->set_list);
 	atomic_set(&set->set_refcount, 1);
 	init_waitqueue_head(&set->set_waitq);