We used to normalize all deltas to equivalents of a 1000dpi mouse before
passing it into the acceleration functions. This has a bunch of drawbacks, not
least that we already have to un-normalize back into device units for a few
devices already (trackpoints, tablet, low-dpi mice).

Switch the filter code over to use device units, relying on the dpi set
earlier during filter creation to convert to normalized. To make things easy,
the output of the filter code is still normalized data, i.e. data ready to be
handed to the libinput caller.

No effective functional changes. For touchpads, we still send normalized
coordinates (for now, anyway). For the various filter methods, we either drop
the places where we unnormalized before or we normalize where needed.

Two possible changes: for trackpoints and low-dpi mice we had a max dpi factor
of 1.0 before - now we don't anymore. This was only the case if a low-dpi
mouse had more than 1000dpi (never true) or a trackpoint had a const accel
lower than 1.0 (yeah, whatever).

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>