Input: add Pegasus Notetaker tablet driver

Input: add Pegasus Notetaker tablet driver

This adds a driver for the Pegasus Notetaker Pen. When connected,
this uses the Pen as an input tablet.

This device was sold in various different brandings, for example
 "Pegasus Mobile Notetaker M210",
 "Genie e-note The Notetaker",
 "Staedtler Digital ballpoint pen 990 01",
 "IRISnotes Express" or
 "NEWLink Digital Note Taker".

Here's an example, so that you know what we are talking about:
http://www.genie-online.de/genie-e-note-2/

https://pegatech.blogspot.com/ seems to be a remaining official resource.

This device can also transfer saved (offline recorded handwritten) data and
there are userspace programs that do this, see https://launchpad.net/m210
(Well, alternatively there are really fast scanners out there :)

It's *really* fun to use as an input tablet though! So let's support this
for everybody.

Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>