Input: atmel_mxt_ts - add calibrate sysfs entry

In some situations, a touch surface may get out of calibration.
It is useful to provide a means for userspace to trigger a recal, so add a
calibrate sysfs entry.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: David Rodero <david@codiguiel.net>
input: atmel_mxt_ts - send a calibration command on system resume

Signed-off-by: David Rodero <david@codiguiel.net>