dev191 - kind of remove DIV_ALWAYS_SET_VOLUME

it's useless crap I put during the Defle compat days
it serves nearly no purpose nowadays

also why is it a command?

src/engine/platform/mmc5.cpp

@@ -327,9 +327,6 @@ int DivPlatformMMC5::dispatch(DivCommand c) {
     case DIV_CMD_MACRO_ON:
       chan[c.chan].std.mask(c.value,false);
       break;
-    case DIV_ALWAYS_SET_VOLUME:
-      return 1;
-      break;
     default:
       break;
   }