only call IPlayerCallback::OnPlayBackSpeedChanged if the speed has actually changed

[vuplus_xbmc] / addons / screensaver.xbmc.builtin.dim / resources / settings.xml

<?xml version="1.0" encoding="utf-8"?>
<settings>
  <setting label="30000" type="slider" id="level" range="20,1,100" default="20"/>
</settings>