Dolphin currently scrolls by the height of three items at a time per "step" when
using a scroll wheel. Because item height is highly variable, this leads to scroll
speed being inconsistent between views, and generally far too fast when using
icon view with icons larger than 22px size.
This patch makes the size of the scroll step based on the text label rather than the
icon size just like D25683, ensuring that the scroll speed does not vary and become
super fast when using large icons in particular.
It also reverts 90beb4a5e37b887caad1e767046a42dad0af1ab3, which is no longer needed.