kingst-la2016: adjust register layout in acquisition configuration

kingst-la2016: adjust register layout in acquisition configuration

The FPGA register space to configure acquisition parameters is unusual
in the sense that some 34bit values are kept in 40bit registers, while
other 32bit values are kept in 24bit registers (stores MSB only). This
answers the question how to communicate a limit of 10 billion samples
in a 32bit register (a doubt about the previous implementation). :)

Reported-By: Kevin Grant <redacted> in github PR 169