Add property for MTE permissive mode.

Bug: 202037138
Change-Id: I272996f124ca8391f9312150d1d8757751fe6acb
diff --git a/private/su.te b/private/su.te
index 587f449..2496473 100644
--- a/private/su.te
+++ b/private/su.te
@@ -27,4 +27,6 @@
   # Do not audit accesses to keystore2 namespace for the su domain.
   dontaudit su keystore2_key_type:{ keystore2 keystore2_key } *;
 
+  # Allow root to set MTE permissive mode.
+  set_prop(su, permissive_mte_prop);
 ')