gpio: aggregator: Remove CONFIG_OF and of_match_ptr() protections

They stop the driver being used with ACPI PRP0001 and are something
I want to avoid being cut and paste into new drivers. Also include
mod_devicetable.h as we struct of_device_id is defined in there.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>