sepolicy: Allow creating synthetic trace events

rss_stat will be throttled using histogram triggers and synthetic trace
events. Add genfs context labels for the synthetic tracefs files.

Bug: 145972256
Test: Check log cat for avc denials
Change-Id: I7e183aa930bb6ee79613d011bed7174d553f9c1a
diff --git a/private/init.te b/private/init.te
index 3b64e25..31dabfa 100644
--- a/private/init.te
+++ b/private/init.te
@@ -107,6 +107,11 @@
 # Allow accessing /sys/kernel/tracing/instances/bootreceiver to set up tracing.
 allow init debugfs_bootreceiver_tracing:file w_file_perms;
 
+# Devices with kernels where CONFIG_HIST_TRIGGERS isn't enabled will
+# attempt to write a non exisiting 'synthetic_events' file, when setting
+# up synthetic events. This is a no-op in tracefs.
+dontaudit init debugfs_tracing_debug:dir { write add_name };
+
 # chown/chmod on devices.
 allow init {
   dev_type