[media] Input: atmel_mxt_ts - add support for T37 diagnostic data

Atmel maXTouch devices have a T37 object which can be used to read raw
touch deltas from the device. This consists of an array of 16-bit
integers, one for each node on the touchscreen matrix.

Signed-off-by: Nick Dyer <nick@shmanahar.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>