Add XML attribute to toggle on/off LocationModePreferenceController.

Test: make RunSettingsRoboTests
ROBOTEST_FILTER=LocationModePreferenceControllerTest all pass.
Bug: 62378711

Change-Id: I0d054171b80b5677dba2a7a02fb076660ed5cc0d

src/com/android/settings/location/LocationModePreferenceController.java

@@ -40,6 +40,11 @@ public class LocationModePreferenceController extends LocationBasePreferenceCont
         return KEY_LOCATION_MODE;
     }
 
+    @Override
+    public boolean isAvailable() {
+        return mContext.getResources().getBoolean(R.bool.config_location_mode_available);
+    }
+
     @Override
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);