iio:adc:max1027: drop of_match_ptr and CONFIG_OF protections

These just prevent the driver being used with ACPI PRP0001
and provide no major benefits.

Part of clearing these out in general in IIO to avoid cut and paste
repetition in new drivers.  Also include mod_devicetable.h as we
directly make use of of_device_id which is defined in there.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Philippe Reynes <tremyfr@yahoo.fr>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>