message: Simplify i915-perf parsing code
  The function read_i915_perf_file() is always present and it's content
  is compiled out, so it's safe to always call it.
diff: @@ -768,12 +768,8 @@ int MainApp::load_etl_file( loading_info_t *loading_info, TraceEvents &trace_eve
  int MainApp::load_i915_perf_file( loading_info_t *loading_info, TraceEvents &trace_events, EventCallback trace_cb )
  {
  -#ifdef USE_I915_PERF
  return read_i915_perf_file( loading_info->filename.c_str(), trace_events.m_strpool,
  trace_events.m_trace_info, &trace_events.i915_perf_reader, trace_cb );
  -#else
  - return 0;
  -#endif
  }
  int SDLCALL MainApp::thread_func( void *data )
  