Remove the systematic bias to the top.

The keyboard used to introduce a systematic bias to the top.
This may have been to compensate an old driver flaw, but it
seems that it is now in the way and causes a lot of mistyped
spaces and backspaces.
This change removes the systematic bias.

Change-Id: Ib65ffba99cbd053d1085d3e6eeaf10a815289fc0