Input: atmel_mxt_ts - read screen config from chip

By reading the touchscreen configuration from the settings that the
maXTouch chip is actually using, we can remove some platform data.

The matrix size is not used for anything, and results in some rather
confusing code to re-read it because it may change when configuration
is downloaded, so don't print it out.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Acked-by: Benson Leung <bleung@chromium.org>
Acked-by: Yufeng Shen <miletus@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>