Input: atmel_mxt_ts - use deep sleep mode when stopped

By writing zero to both the active and idle cycle times the maXTouch device
is put into a deep sleep mode when it consumes minimal power. It is
unnecessary to change the configuration of any other objects (for example
to disable T9 touchscreen).

It is counterproductive to reset the chip on resume, it will result in a
long delay. However it is necessary to issue a calibrate command after the
chip has spent any time in deep sleep.

This patch also deals with the situation where the power configuration is
zero on probe, which would mean that the device never wakes up to execute
commands.

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>