Add `su_key`, a keystore2_key namespace for `su`.

Add a keystore2_key namespace that can be used by `su` for testing.

Test: keystore2_test
Bug: 158500146
Bug: 160623310
Bug: 159466840
Change-Id: I017a10ad8c7fce28e8bc921b764e65c49bae5107
Merged-In: I017a10ad8c7fce28e8bc921b764e65c49bae5107
diff --git a/private/su.te b/private/su.te
index 16e47bb..072e8db 100644
--- a/private/su.te
+++ b/private/su.te
@@ -20,4 +20,8 @@
   permissive su;
 
   app_domain(su)
+
+  # Do not audit accesses to keystore2 namespace for the su domain.
+  dontaudit su keystore2_key_type:{ keystore2 keystore2_key } *;
+
 ')