Various small audren fixes (#894)

* Remove redundant modulo on wave buffer index

This is already performed by SetBufferIndex

* Correct typo in UpdateDataHeader

MixeSize -> MixSize

* Remove unused variable in audren

'volume' was unused and 'voice.Volume' was used instead so remove 'volume'

Ryujinx.HLE/HOS/Services/Audio/AudioRendererManager/IAudioRenderer.cs

@@ -346,7 +346,6 @@ namespace Ryujinx.HLE.HOS.Services.Audio.AudioRendererManager
 
                 int   outOffset      = 0;
                 int   pendingSamples = MixBufferSamplesCount;
-                float volume         = voice.Volume;
 
                 while (pendingSamples > 0)
                 {

Ryujinx.HLE/HOS/Services/Audio/AudioRendererManager/Types/UpdateDataHeader.cs

@@ -8,7 +8,7 @@
         public int VoiceSize;
         public int VoiceResourceSize;
         public int EffectSize;
-        public int MixeSize;
+        public int MixSize;
         public int SinkSize;
         public int PerformanceManagerSize;
         public int Unknown24;

Ryujinx.HLE/HOS/Services/Audio/AudioRendererManager/VoiceContext.cs

@@ -108,7 +108,7 @@ namespace Ryujinx.HLE.HOS.Services.Audio.AudioRendererManager
 
                 if (wb.Looping == 0)
                 {
-                    SetBufferIndex((_bufferIndex + 1) & 3);
+                    SetBufferIndex(_bufferIndex + 1);
                 }
 
                 _outStatus.PlayedWaveBuffersCount++;