enable shutdown button for AXP192 only

app/src/main/java/com/geeksville/mesh/model/UIState.kt

@@ -204,6 +204,11 @@ class UIViewModel @Inject constructor(
     // We consider hasWifi = ESP32
     var isESP32: Boolean = _localConfig.value?.hasWifi() == true
 
+    fun hasAXP(): Boolean {
+        val hasAXP = listOf(4, 7, 9) // mesh.proto 'HardwareModel' enums with AXP192 chip
+        return hasAXP.contains(nodeDB.ourNodeInfo?.user?.hwModel?.number)
+    }
+
     /// hardware info about our local device (can be null)
     private val _myNodeInfo = MutableLiveData<MyNodeInfo?>()
     val myNodeInfo: LiveData<MyNodeInfo?> get() = _myNodeInfo

app/src/main/java/com/geeksville/mesh/ui/AdvancedSettingsFragment.kt

@@ -53,7 +53,7 @@ class AdvancedSettingsFragment : ScreenFragment("Advanced Settings"), Logging {
             binding.lsSleepView.isEnabled = connected && model.isPowerSaving ?: false
             binding.positionBroadcastSwitch.isEnabled = connected
             binding.lsSleepSwitch.isEnabled = connected && model.isESP32
-            binding.shutdownButton.isEnabled = connected
+            binding.shutdownButton.isEnabled = connected && model.hasAXP()
             binding.rebootButton.isEnabled = connected
         }