input/logicport: don't re-create channels after input module reset

input/logicport: don't re-create channels after input module reset

Split the creation of channels and groups as well as the creation of the
session feed buffer into separate routines. Re-allocate the buffer after
reset but do not re-create the channels and groups.

This implementation assumes that after reset() of the input module, the
very same set of channels (including their order, names and enabled
state, as well as group membership) results from processing the
subsequently fed file content. Reading rather different configurations
from the same input file by means of repeated reset and re-read may not
work as expected.