access_vectors: add lockdown class

Needed to support upstream patch
https://github.com/torvalds/linux/commit/59438b46471ae6cdfb761afc8c9beaf1e428a331

Bug: 148822198
Test: compiles
Change-Id: I304c1a97c12067dd08d4ceef93702101908012ed
diff --git a/private/access_vectors b/private/access_vectors
index aa0109c..4144be8 100644
--- a/private/access_vectors
+++ b/private/access_vectors
@@ -733,3 +733,9 @@
 	read
 	write
 }
+
+class lockdown
+{
+	integrity
+	confidentiality
+}