[XMP] Fixed issue with xmp_default_volume not being correctly applied

- Added menu to modify XMP volume and state

src/xenia/apu/audio_media_player.h

@@ -106,7 +106,7 @@ class AudioMediaPlayer {
   XmpApp::PlaybackMode playback_mode_ = XmpApp::PlaybackMode::kInOrder;
   XmpApp::RepeatMode repeat_mode_ = XmpApp::RepeatMode::kPlaylist;
   XmpApp::PlaybackFlags playback_flags_ = XmpApp::PlaybackFlags::kDefault;
-  float volume_ = 1.0f;
+  float volume_ = 0.0f;
   uint32_t dash_init_state = 0;
 
   std::unordered_map<uint32_t, std::unique_ptr<XmpApp::Playlist>> playlists_;