This adds a struct eeti_ts_platform_data which currently holds only one
value to specify the interrupt polarity.

The driver has a fallback if no platform data is passed in via the
i2c_board_info, so no regression is caused.
Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>