Replace 'Expand DRAM' option with dropdown menu (#32)

Allows to use mods that require a larger memory pool to allocate from.

src/Ryujinx/UI/ViewModels/Input/InputViewModel.cs

@@ -45,7 +45,7 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
 
         private PlayerIndex _playerId;
         private int _controller;
-        private int _controllerNumber;
+        private readonly int _controllerNumber;
         private string _controllerImage;
         private int _device;
         private object _configViewModel;