Remove unused SetUpdateCallback. We set the update callback on start.

smx-config/CurrentSMXDevice.cs

@@ -80,7 +80,6 @@ namespace smx_config
 
         public void Shutdown()
         {
-            SMX.SMX.SetUpdateCallback(null);
             SMX.SMX.Stop();
         }
 

smx-config/SMX.cs

@@ -240,11 +240,6 @@ namespace SMX
         [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
         public delegate void InternalUpdateCallback(int PadNumber, int reason, IntPtr user);
         private static InternalUpdateCallback CurrentUpdateCallback;
-        public static void SetUpdateCallback(UpdateCallback callback)
-        {
-            if(!DLLAvailable()) return;
-
-        }
 
         public static void Start(UpdateCallback callback)
         {