touchpad: Drop the scroll direction lock, increase threshold instead

The direction lock was intended to avoid erroneous horizontal scroll events
when scrolling vertically (and vice versa). Some testing on my touchpad here
shows that it is too easy to accidentally lock the direction when no lock is
intended (e.g. moving around an image). And quite hard to figure out what a
pure vertical gesture is.

I get movements from 90 degrees to 70 degrees for something my brain would
consider vertical scrolling. Depending on the hand position, the fingers
actually perform a slight curve, not a straight line.

Hence - drop the direction lock, but increase the threshold a little. It
doesn't totally avoid horizontal scroll events but keeps them minimal.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
touchpad: whitespace fix

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