skins2: fix equalizer

Recent change in core(audio) now requires playlist to be passed as object
so that findAout can success (based on "find-input-callback" inheritance)

modules/gui/skins2/commands/cmd_audio.cpp

@@ -30,7 +30,9 @@
 
 void CmdSetEqualizer::execute()
 {
-    aout_EnableFilter( getIntf(), "equalizer", m_enable );
+    playlist_t* pPlaylist = getIntf()->p_sys->p_playlist;
+
+    aout_EnableFilter( pPlaylist, "equalizer", m_enable );
     VlcProc::instance( getIntf() )->update_equalizer();
 }