Fix crashloop in CarStatusBar.

System ui seems to be undergoing a refactor to bring in
dependency injection, in the process, mBatteryController
in CarStatusBar was not being set, causing a NPE.

Since it looks like the work is still ongoing, this is
just a spot fix for the crash, once the dependency injection
migration is complete, we can reexamine the CarStatusBar
implementation.

Bug: 34633087
Test: Verified that system booted correctly.
Change-Id: Idd3e0286fd87196ae572349904d5bef744d54353

packages/SystemUI/src/com/android/systemui/statusbar/car/CarStatusBar.java

@@ -72,6 +72,7 @@ public class CarStatusBar extends PhoneStatusBar implements
         SystemServicesProxy.getInstance(mContext).registerTaskStackListener(mTaskStackListener);
         registerPackageChangeReceivers();
 
+        createBatteryController();
         mCarBatteryController.startListening();
         mConnectedDeviceSignalController.startListening();
     }
@@ -113,8 +114,7 @@ public class CarStatusBar extends PhoneStatusBar implements
         return statusBarView;
     }
 
-    @Override
-    protected BatteryController createBatteryController() {
+    private BatteryController createBatteryController() {
         mCarBatteryController = new CarBatteryController(mContext);
         mCarBatteryController.addBatteryViewHandler(this);
         return mCarBatteryController;

packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java

@@ -989,10 +989,6 @@ public class PhoneStatusBar extends BaseStatusBar implements DemoMode,
         }
     }
 
-    protected BatteryController createBatteryController() {
-        return new BatteryControllerImpl(mContext);
-    }
-
     private void inflateShelf() {
         mNotificationShelf =
                 (NotificationShelf) LayoutInflater.from(mContext).inflate(