thermald: make CPU usage list a constant size (#31526)

selfdrive/thermald/thermald.py

@@ -245,8 +245,10 @@ def thermald_thread(end_event, hw_queue) -> None:
 
     msg.deviceState.freeSpacePercent = get_available_percent(default=100.0)
     msg.deviceState.memoryUsagePercent = int(round(psutil.virtual_memory().percent))
-    msg.deviceState.cpuUsagePercent = [int(round(n)) for n in psutil.cpu_percent(percpu=True)]
     msg.deviceState.gpuUsagePercent = int(round(HARDWARE.get_gpu_usage_percent()))
+    online_cpu_usage = [int(round(n)) for n in psutil.cpu_percent(percpu=True)]
+    offline_cpu_usage = [0., ] * (len(msg.deviceState.cpuTempC) - len(online_cpu_usage))
+    msg.deviceState.cpuUsagePercent = online_cpu_usage + offline_cpu_usage
 
     msg.deviceState.networkType = last_hw_state.network_type
     msg.deviceState.networkMetered = last_hw_state.network_metered