Disable recyclerview caching for lowend devices

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -509,6 +509,9 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
         });
 
         rvMessage.setHasFixedSize(false);
+
+        int threads = prefs.getInt("query_threads", 4);
+        if (threads >= 4)
             rvMessage.setItemViewCacheSize(10); // Default: 2
         //rvMessage.getRecycledViewPool().setMaxRecycledViews(0, 10); // Default 5