Input: add sur40 driver for Samsung SUR40 (aka MS Surface 2.0/Pixelsense)

This patch adds support for the built-in multitouch sensor in the Samsung
SUR40 touchscreen device, also known as Microsoft Surface 2.0 or Microsoft
Pixelsense. Support for raw video output from the sensor as well as the
accelerometer will be added in a later patch.

Signed-off-by: Florian Echtler <floe@butterbrot.org>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>