gpiolib: acpi: Add missing memset(0) to acpi_get_gpiod_from_data()

When refactoring the acpi_get_gpiod_from_data() the change missed
cleaning up the variable on stack. Add missing memset().

Reported-by: Ferry Toth <ftoth@exalondelft.nl>
Fixes: 16ba046e

 ("gpiolib: acpi: teach acpi_find_gpio() to handle data-only nodes")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>