[Hashing] Decrypt Nintendo DS header during hashing if encrypted

[Sanaki]

Nintendo DS games are equally playable both encrypted and decrypted. Only about 2KiB of data is affected by the encryption, but unfortunately that section is hashed. Given that systems capable of emulating NDS are easily strong enough to handle the decryption quickly, I suggest we decrypt as part of the hashing process for encrypted roms.

Reference code:
https://github.com/SabreTools/NDecrypt/tree/master/NDecrypt/NDS
https://github.com/TuxSH/wooddumper/tree/master/woodsec