[test, systemtest] Add DIF AON smoketest to CI

Signed-off-by: Silvestrs Timofejevs <silvestrst@lowrisc.org>
diff --git a/test/systemtest/config.py b/test/systemtest/config.py
index 590b7b2..0a5b6fa 100644
--- a/test/systemtest/config.py
+++ b/test/systemtest/config.py
@@ -49,6 +49,9 @@
         "name": "dif_aes_smoketest",
     },
     {
+        "name": "dif_aon_timer_smoketest",
+    },
+    {
         "name": "dif_otp_ctrl_smoketest",
     },
     {