dd BTN_TOUCH events

Add BTN_TOUCH event reporting to ucb1400_ts and accelerated mainstone-wm97xx
touchscreen drivers. Together with previously posted similar patch for
wm97xx-core this will make all touchscreen drivers behave consistently wrt.
BTN_TOUCH.

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
såèû˜