gpiolib: acpi: support bias pull disable

On top of looking at PULL_UP and PULL_DOWN flags, also look at
PULL_DISABLE and set the appropriate GPIO flag. The GPIO core will then
pass down this to controllers that support it.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>