Input: sun4i-ts - allow controlling filter and sensitivity via DT

This commit introduces two new optional device-tree properties:
"tp-sensitive-adjust": adjust sensitivity of pen down detection
"filter-type": select median and averaging filter

The previous fixed defaults, didn't work well for the Olimex
A13-LCD10TS (I have).

Signed-off-by: Jens Thiele <karme@karme.de>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>