Input: Add ATMEL QT602240 touchscreen driver

The chip's full name is AT42QT602240 or ATMXT224. This is a capacitive
touchscreen supporting 10-contact multitouch and using I2C interface.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>