Remove some old code and do an a=a to trick a compiler in non-debug mode

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@4293

src/hardware/sblaster.cpp

@@ -707,6 +707,8 @@ static void DSP_DoDMATransfer(DMA_MODES mode,Bitu freq,bool autoinit, bool stere
 		autoinit ? "Auto-Init" : "Single-Cycle",
 		freq, sb.dma.rate, sb.dma.left
 		);
+#else
+	type = type;
 #endif
 }