Input: atmel_mxt_ts - use more managed resources

Switch mxt_data and interrupt to resource managed allocation methods,
which cleans up the driver slightly and prepares for adding
reset GPIO support.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>