filter: don't normalize the const filter approach

filter: don't normalize the const filter approach

The filter vs const filter is supposed to be for accelerated vs
non-accelerated motion (e.g. pointer motion vs scrolling) - in both
cases the returned value is supposed to be in the same coordinate
system, just once with an extra accel factor applied.

This was broken in the flat and low-dpi profiles: in both of those the
accelerated filter does *not* normalize, it merely applies the fixed/adaptive factor.
The constant filter normalized however. The result was that on e.g. a
5000dpi mouse the constant motion was 5 times slower than the
accelerated motion, even with a factor of 1.

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