[XMA] Revert changes in old XMA decoder to state from master repository.

- If you have new issues with sound it is recommended to switch to new decoder.

src/xenia/apu/xma_context_old.h

@@ -66,10 +66,6 @@ class XmaContextOld : public XmaContext {
   void Decode(XMA_CONTEXT_DATA* data);
   int PrepareDecoder(uint8_t* packet, int sample_rate, bool is_two_channel);
 
-  // This method should be used ONLY when we're at the last packet of the stream
-  // and we want to find offset in next buffer
-  uint32_t GetPacketFirstFrameOffset(const XMA_CONTEXT_DATA* data);
-
   // uint32_t decoded_consumed_samples_ = 0; // TODO do this dynamically
   // int decoded_idx_ = -1;