staging/lustre: fix sparse warning

Fix sparse complaint: "Using plain integer as NULL pointer"
Signed-off-by: Denis Pithon <denis.pithon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ptlrpc/sec.c

@@ -354,7 +354,7 @@ static int import_sec_check_expire(struct obd_import *imp)
 		return 0;
 
 	CDEBUG(D_SEC, "found delayed sec adapt expired, do it now\n");
-	return sptlrpc_import_sec_adapt(imp, NULL, 0);
+	return sptlrpc_import_sec_adapt(imp, NULL, NULL);
 }
 
 static int import_sec_validate_get(struct obd_import *imp,