xfree86: Use different scroll increment than libinput in inputtest drv

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
4 jobs for xfree86-inputtest-fixes in 3 minutes and 36 seconds (queued for 1 second)
Status Name Job ID Coverage
  Docker Image
passed debian-buster #6251692

00:00:13

 
  Build And Test
passed autotools #6251693

00:03:22

passed meson #6251694

00:02:37

passed meson-noglamor #6251695

00:02:22