kingst-la2016: adjust sample memory interpretation for LA5032

The 32-channel model in the Kingst LA series uses a different sample
memory layout than 16-channel models. The previously encoded assumption
of 3x (u32 + u8) to hold 32 channels within the same 15 bytes as other
models was incorrect. User feedback in bug #1805 suggests that the
transfer size and the sequence number size differs as well. Thus the
packet count per transfer differs, too. LA5032 holds 6 packets within
a transfer that spans 32 bytes.

Reported-By: Roman Shishkin <redacted>