Input: add driver for SiS 9200 family I2C touchscreen controllers

This is a driver for SiS 9200 family touchscreen controllers using I2C bus.

Signed-off-by: Mika Penttilä <mika.penttila@nextfour.com>
Acked-by: Tammy Tseng <tammy_tseng@sis.com>
Acked-by: Yuger Yu <yuger_yu@sis.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>