[FileTools] Stop xxHash from writing on standard DFD

From erroneous xxHash calculations, I also determined that the hash length is 8 characters, similar to CRC hashes

SabreTools.Helper/Tools/FileTools.cs

@@ -611,7 +611,7 @@ namespace SabreTools.Helper.Tools
 				}
 				if ((omitFromScan & Hash.xxHash) == 0)
 				{
-					rom.SHA512 = xxHash.Digest().ToString("X").ToLowerInvariant(); // TODO: Not sure how long xxHash is supposed to be. Add the length here and in constants later
+					//rom.xxHash = xxHash.Digest().ToString("X8").ToLowerInvariant();
 				}
 
 				// Dispose of the hashers