filter: move the pointer acceleration profiles back to units/ms

filter: move the pointer acceleration profiles back to units/ms

There is no need here to use µs since we're just handling speeds/thresholds,
not actual events where a ms granularity can be too high.

Moving back to ms lets us drop a bunch of zeroes that clutter up the code, and
since the acceleration functions are a bit magic anyway, having the various
1000.0 factors in there makes it even less obvious.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>