Input: atmel_mxt_ts - implement CRC check for configuration data

The configuration is stored in NVRAM on the maXTouch chip. When the device
is reset it reports a CRC of the stored configuration values. Therefore it
isn't necessary to send the configuration on each probe - we can check the
CRC matches and avoid a timeconsuming backup/reset cycle.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Acked-by: Benson Leung <bleung@chromium.org>
Acked-by: Yufeng Shen <miletus@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>