filter: revamp to create device-specific filters, rather than accel functions

filter: revamp to create device-specific filters, rather than accel functions

The previous approach to pointer acceleration was to initialize the same
motion filter behavior but a different acceleration profile depending on the
hardware (the profile converts a speed to a multiplier for input deltas).

To be more flexible for hardware-specifics, change this into a set of specific
pointer acceleration init functions. This patch has no effective functional
changes, they're still all the same.

The acceleration functions are kept for direct access by the ptraccel-debug
tool.

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