gpio: acpi: Factor out acpi_gpio_to_gpiod_flags() helper

The helper function acpi_gpio_to_gpiod_flags() will be used later to configure
pin properly whenever it's requested.

While here, introduce a checking error code returned by gpiod_configure_flags()
and bail out if it's not okay.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>