perfetto: Add Panfrost data sources to system.cfg

Just like for msm and i915, so it works out-of-the-box.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28363>

src/tool/pps/cfg/system.cfg

@@ -58,6 +58,15 @@ data_sources {
   }
 }
 
+data_sources {
+  config {
+    name: "gpu.counters.panfrost"
+    gpu_counter_config {
+      counter_period_ns: 100000
+    }
+  }
+}
+
 data_sources {
   config {
     name: "track_event"