Scroll to item if it's not visible on keyPress

Summary: Always scroll to item if it's not visible on keyPress, even if it's the current index.

Test Plan: Select the last item, scroll up to make it not visible > press the `End` key > Dolphin now scrolls to that item.

Reviewers: #dolphin, ngraham, elvisangelaccio

Reviewed By: #dolphin, ngraham, elvisangelaccio

Subscribers: elvisangelaccio, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D20152