MAINTAINERS: Update GPIO ACPI library to Supported

The actual status of the code is Supported.

Reported-by:  <dave.hansen@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>