drivers: input: atmel: fix chip calibration

qt_time_point was always 0, so check_abs_time() always returned 1
and the calibration was considered good even when it wasn't.
Revert "drivers: touchscreen: make driver filter optional"

The difference is barely noticeable, there's no need to provide an
option to disable it.

This reverts commit 24cc0eb45626531da6f95395ccfc9b6e08d90011.
drivers: input: atmel: make chip calibration optional

Calibrations must be performed with a clean and dried screen.
Offer the user the possibility to disable calibrations in order
to prevent miscalibrations. Chip calibrations are not required.

Disable calibrations by default to prevent issues.
An initial miscalibration will badly affect the behaviour of the
touchscreen until a new calibration is performed, which could never
happen in case the user disabled it.