Make tombstones 664.

They are still restricted by SELinux, and apps still cannot open them
because they don't have `open` SELinux permission.

Bug: 312740614
Change-Id: I83b7e6ed39f5af64f161af3b3e8e33af0d125b20
diff --git a/rootdir/init.rc b/rootdir/init.rc
index f3b2d03..3c367f9 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -709,7 +709,7 @@
 
     # Start tombstoned early to be able to store tombstones.
     mkdir /data/anr 0775 system system encryption=Require
-    mkdir /data/tombstones 0771 system system encryption=Require
+    mkdir /data/tombstones 0775 system system encryption=Require
     mkdir /data/vendor/tombstones 0771 root root
     mkdir /data/vendor/tombstones/wifi 0771 wifi wifi
     start tombstoned