Revert "QAIV - Fix scollbars with ScrollPerPixel to scroll 1 pixel."

This reverts commit 934f06220391eb0e0ebf66a2eb037f48adb4c43c.

The patch needs to be modified a bit. Many users considers
not having the old feature as a big regression.

The feature needs to be improved with a variable that is
only set when the user uses setSingleStep.

Task-number: QTBUG-33906

Change-Id: I35e5d3e9d3d7a3ebd01807b03a0e7a424185d483
Reviewed-by: Thorbjørn Lindeijer <bjorn@lindeijer.nl>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>