NES: Fix battery backup in certain bootgod identified games

If the wram with the battery backup on it is internal to the mapper asic, and not a separate ram chip, bootgod will have <chip battery=1> and not <wram battery=1>.  Fixes #2570.

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/BootGodDB.cs

@@ -118,6 +118,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 									break;
 								case "chip":
 									currCart.Chips.Add(xmlReader.GetAttribute("type"));
+									if (xmlReader.GetAttribute("battery") != null)
+										currCart.WramBattery = true;
 									break;
 							}
 						} else