We currently have three keyboard scanning drivers in the code base
(npcx, it8xxx2 and mchp_xec, last two yet to be converted to input).
These have been largely copy pasted from each other and share a lot of
the same structure and code.
This PR lays a foundation to start decoupling feature from those drivers
into a common code base, and it is heavily inspired by the current
regulator common data/config one.
Feature wise this only moves the thread struct, stack and initialization
to the common code and declares the thread callback as the only API, but
the intent is to move as much code as possible in there an only abstract
device specific callbacks in the api structures.
Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
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