This reverts commit d90b5f8301.
Reverting for two reasons:
* the scaling does not work on devices that don't advertise resolution, and
the default resolution used (100 units/mm) is higher than most devices,
resulting in a significant slowdown of the touchpads.
* the scaling is still affected by resolution changing. The patch worked
before acceleration but since it maps into resolution-dependent dx/dy
coordinates the acceleration may distort the movement after the fact. So the
same input data generates different movements depending on the resolution.
This can't easily be fixed for all affected devices as synaptics has its own
velocity calculation method whereas wacom doesn't. So anything in the server
won't work for both at the same time.
Revert this for now, until a more integrated solution can be implemented.