mmd: allow to write stats

mmd sends statistics about zram.

Bug: 392783537
Test: statsd_testdrive

Change-Id: I07492d2c5b3117cfd70936a1ef857452a10855db
diff --git a/private/mmd.te b/private/mmd.te
index 90510f1..69f12fc 100644
--- a/private/mmd.te
+++ b/private/mmd.te
@@ -29,3 +29,6 @@
 
 # swapon syscall
 allow mmd self:capability sys_admin;
+
+# Allow mmd to write to statsd socket.
+unix_socket_send(mmd, statsdw, statsd)