Centralize logic to detect when the DPL2 decoder should be used.

Source/Core/AudioCommon/CubebStream.cpp

@@ -37,7 +37,7 @@ bool CubebStream::Init()
   if (!m_ctx)
     return false;
 
-  m_stereo = !SConfig::GetInstance().bDPL2Decoder || SConfig::GetInstance().bDSPHLE;
+  m_stereo = !SConfig::GetInstance().ShouldUseDPL2Decoder();
 
   cubeb_stream_params params;
   params.rate = m_mixer->GetSampleRate();

Source/Core/AudioCommon/OpenALStream.cpp

@@ -221,8 +221,7 @@ void OpenALStream::SoundLoop()
 
   bool float32_capable = palIsExtensionPresent("AL_EXT_float32") != 0;
   bool surround_capable = palIsExtensionPresent("AL_EXT_MCFORMATS") || IsCreativeXFi();
-  bool use_surround =
-      SConfig::GetInstance().bDPL2Decoder && surround_capable && !SConfig::GetInstance().bDSPHLE;
+  bool use_surround = SConfig::GetInstance().ShouldUseDPL2Decoder() && surround_capable;
 
   // As there is no extension to check for 32-bit fixed point support
   // and we know that only a X-Fi with hardware OpenAL supports it,

Source/Core/AudioCommon/PulseAudioStream.cpp

@@ -19,7 +19,7 @@ PulseAudio::PulseAudio() = default;
 
 bool PulseAudio::Init()
 {
-  m_stereo = !SConfig::GetInstance().bDPL2Decoder || SConfig::GetInstance().bDSPHLE;
+  m_stereo = !SConfig::GetInstance().ShouldUseDPL2Decoder();
   m_channels = m_stereo ? 2 : 6;  // will tell PA we use a Stereo or 5.0 channel setup
 
   NOTICE_LOG(AUDIO, "PulseAudio backend using %d channels", m_channels);

Source/Core/Core/ConfigManager.cpp

@@ -1063,3 +1063,8 @@ IniFile SConfig::LoadGameIni(const std::string& id, std::optional<u16> revision)
     game_ini.Load(File::GetUserPath(D_GAMESETTINGS_IDX) + filename, true);
   return game_ini;
 }
+
+bool SConfig::ShouldUseDPL2Decoder() const
+{
+  return bDPL2Decoder && !bDSPHLE;
+}

Source/Core/Core/ConfigManager.h

@@ -173,6 +173,9 @@ struct SConfig
   bool bEnableCustomRTC;
   u32 m_customRTCValue;
 
+  // DPL2
+  bool ShouldUseDPL2Decoder() const;
+
   DiscIO::Region m_region;
 
   std::string m_strVideoBackend;