The common device structure was used only for sharing the fingerprint
and layout descriptor, but the nemo backend doesn't even store a layout
descriptor, and the fingerprint can equally well be passed around as a
function argument.
The memory layout of the Mares Puck and Nemo devices is very similar,
which allows to share the parsing code between the backends.
The Mares Puck protocol allows for a more efficient implementation, by
reading only the data that we really need. But as an intermediate
solution, reusing the Nemo code is good enough.
