Add /dev/__properties__/property_info

Allow init to create a serialized property_info file and allow all
processes to read it.

Bug: 36001741
Test: boot bullhead, walleye using property_info

Change-Id: Ie51d4c0f0221b128dd087029c811fda15b4d7093
diff --git a/private/file_contexts b/private/file_contexts
index ec7d246..3c6642a 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -171,6 +171,7 @@
 /dev/xt_qtaguid	u:object_r:qtaguid_device:s0
 /dev/zero		u:object_r:zero_device:s0
 /dev/__properties__ u:object_r:properties_device:s0
+/dev/__properties__/property_info   u:object_r:property_info:s0
 #############################
 # System files
 #