Core: Switch controller interface to render widget on booting

Previously, the Qt frontend would initialize the controller
interface on starting, resulting in the cursor position being
relative to the main window, instead of the render window.

Source/Core/InputCommon/ControllerInterface/ControllerInterface.cpp

@@ -80,6 +80,15 @@ void ControllerInterface::Initialize(const WindowSystemInfo& wsi)
   RefreshDevices();
 }
 
+void ControllerInterface::ChangeWindow(void* hwnd)
+{
+  if (!m_is_init)
+    return;
+
+  m_wsi.render_surface = hwnd;
+  RefreshDevices();
+}
+
 void ControllerInterface::RefreshDevices()
 {
   if (!m_is_init)