HID: lenovo: Use native middle-button mode for compact keyboards

By default the middle button is in a compatibility mode, and generates
middle-button and wheel events on pressing and pressing and dragging.
Unfortunately this is buggy:
* The middle button comes up before starting wheel events, causing a middle
  click on whatever the mouse cursor was sitting on
* The USB keyboard generates the wrong horizontal wheel event

Instead, enable the mode the Windows driver uses, and add support for the
custom events this generates. We still get an unwanted middle-click, but it's
after the scroll.

Signed-off-by: Jamie Lentin <jm@lentin.co.uk>
Apparently all that report shenannigans wasn't needed. bah.