Input: qt602240_ts - rename to atmel_mxt_ts

Since the driver will be supporting whole range of Atmels mXT touchscreen
controllers we better rename it to atmel_mxt_ts.

Acked-by: Iiro Valkonen <iiro.valkonen@atmel.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>