pinctrl: intel: Add __intel_gpio_get_direction() helper

Add __intel_gpio_get_direction() helper which provides all possible
physical states of the pad.

With that done, update current users and make the respective checks
consistent.

While at it, make the style of anonymous enum kernel documentation
consistent.

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>