There is quite a wide spread in the delta events generated by trackpoints,
some generate deltas of 1-2 under normal use, while others generate deltas
from 1-20.

It is desirable to normalize trackpoint deltas just like we are normalizing
mouse deltas to 1000 dpi, so as to give different model laptops aprox.
the same trackpoint cursor speed ootb.

Recent versions of udev + hwdb set a POINTINGSTICK_CONST_ACCEL udev property
which can be used to adjust trackpoints which are too slow / too fast
ootb, this commit implements support for that property.

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