change mapper 12 (mmc3 variant) to specify MMC3A chip version. this is necessary to fix dragon ball Z 5, and since this is the only game I know of that uses mapper 12, it should be safe. however, if games are being broken by not knowing the right mmc3 variant then we'd need to add it to a game hash table or set it in the cartinfo struct so that mapper init can deal with it. support in fceux for mmc3 chip variant irq behaviours are minimal. this fixes #3516274

src/boards/mmc3.cpp

@@ -398,6 +398,8 @@ void Mapper12_Init(CartInfo *info)
 {
  GenMMC3_Init(info, 512, 256, 8, info->battery);
  cwrap=M12CW;
+ isRevB=0;
+
  info->Power=M12Power;
  AddExState(EXPREGS, 2, 0, "EXPR");
 }