kingst-la2016: rephrase manufacture date and device type support

kingst-la2016: rephrase manufacture date and device type support

The "purchase date" reader asssumed a little endian host when reading
16bit data from the device. Use endianess aware readers instead. Which
also unobfuscates the YY and MM positions in the byte array (comments
were plenty, but the code would not reflect what happened). Rephrase
the consistency check in the date and magic code paths (the inverted
bits), better reflect the XOR approach.

Prefer the "manufacture date" term since that's what the vendor is aware
of, while the customer's date of purchase or the dealer's shelf time are
unknown to vendors.

Split complex invocation from caller's flow control to improve
readability of the code path. Which also trims text line length.