gpiolib: acpi: avoid leaking ACPI details into upper gpiolib layers

There is no need for the generic parts of GPIOLIB to be aware of
implementation details of ACPI-bases lookups.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>