Classify pointing sticks using the input property

BUG=chromium:1114828
TEST=With other CLs in Gestures library and Chromium, check pointing
     stick settings can be changed independently.

Cq-Depend: chromium:2486866
Change-Id: I17c859b8d3da81f52b488c7545a2847b894726ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/libevdev/+/2487202
Reviewed-by: Sean O'Brien <seobrien@chromium.org>
Tested-by: Harry Cutts <hcutts@chromium.org>
Commit-Queue: Harry Cutts <hcutts@chromium.org>