Input: add driver for FT5x06 based EDT displays

This is a driver for the EDT "Polytouch" family of touch controllers
based on the FocalTech FT5x06 line of chips.

Signed-off-by: Simon Budig <simon.budig@kernelconcepts.de>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>