ControllerInterface: Adjust sort priorities to ensure default keyboard-mouse device is first.

Source/Core/InputCommon/ControllerInterface/Xlib/XInput2.cpp

@@ -414,6 +414,11 @@ std::string KeyboardMouse::GetSource() const
   return std::string(SOURCE_NAME);
 }
 
+int KeyboardMouse::GetSortPriority() const
+{
+  return DEFAULT_DEVICE_SORT_PRIORITY;
+}
+
 KeyboardMouse::Key::Key(Display* const display, KeyCode keycode, const char* keyboard)
     : m_display(display), m_keyboard(keyboard), m_keycode(keycode)
 {