Update Wi-Fi Wakeup setting to check whether the feature is available.

Bug: 38037361
Test: make ROBOTEST_FILTER=WifiWakeupPreferenceControllerTest
RunSettingsRoboTests -j40

Change-Id: I1c1b930546cc090d72f3047058a428acd1b2883a

src/com/android/settings/wifi/WifiWakeupPreferenceController.java

@@ -70,7 +70,10 @@ public class WifiWakeupPreferenceController extends PreferenceController impleme
 
     @Override
     public boolean isAvailable() {
-        return true;
+        final int defaultValue = mContext.getResources().getInteger(
+                com.android.internal.R.integer.config_wifi_wakeup_available);
+        return Settings.Global.getInt(mContext.getContentResolver(),
+                Settings.Global.WIFI_WAKEUP_AVAILABLE, defaultValue) == 1;
     }
 
     @Override