Input: cyttsp - perform hard reset of the chip during probe

Since we removed support for calling an init() callback from
the platform data, introduce a function which initializes
the chip by performing a hard reset, using the reset gpio
defined in the device properties.

Signed-off-by: Oreste Salerno <oreste.salerno@tomtom.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>