hameg-hmo: Map logic data from second digital pod to channels D8-D15

hameg-hmo: Map logic data from second digital pod to channels D8-D15

An internal libsigrok implementation detail prevents partial submission
of logic data for different channel groups in multiple calls. Instead
one logic packet needs to be sent in a single call, which combines data
for all channels.

Introduce a logic data storage which folds samples from several channel
groups that were received at different points in time into a combined
memory layout of larger unitsize. Stick with the former shortcut of
passing on the input bytes directly when only the first digital pod is
used during acquisition.

This change correctly maps data from the second pod to channels D8-D15.