Previously, touchpad deltas were converted to 1000-dpi normalized coordinates
and handled from there. This changed in bdd4264d

 (1.6)
when the filter functions started taking device coordinates instead. Since
then, we used to convert the device delta to normalized coordinates, then
(often immediately) convert back to device coordinates, albeit for equal x/y
resolution. This isn't necessary, we can just convert the device coordinates
to x/y-equal resolution device coordinates and pass those on.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>