Don't mute Sound Blaster DSP output when DMA disabled. Fixes use of SB Direct Output.

src/sound_sb_dsp.c

@@ -1110,8 +1110,7 @@ void sb_poll_i(void *p)
 
 void sb_dsp_update(sb_dsp_t *dsp)
 {
-        /*this "if" implements two things: speaker on/off and buffer cleanup after stopping audio. */
-        if (!dsp->sbenable || dsp->muted)
+        if (dsp->muted)
         {
                 dsp->sbdatl=0;
                 dsp->sbdatr=0;