Pad dsp_t to keep savestates compatibility

Remove some unused DSP regs to avoid changing the size of dsp_t, which
breaks serialization compatibility.

core/hw/aica/dsp.h

@@ -64,10 +64,7 @@ struct dsp_t
 	//various dsp regs
 	signed int ACC;        //26 bit
 	signed int SHIFTED;    //24 bit
-	signed int X;          //24 bit
-	signed int Y;          //13 bit
 	signed int B;          //26 bit
-	signed int INPUTS;     //24 bit
 	signed int MEMVAL[4];
 	signed int FRC_REG;    //13 bit
 	signed int Y_REG;      //24 bit