Input: adxl34x - make it enumerable in ACPI environment

The ACPI-enabled platform may contain _DSD method to enable this driver
using compatible string.

Remove OF specifics to re-use existing code on ACPI-enabled platforms.

Suggested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>