pinctrl: lynxpoint: Implement intel_gpio_get_direction callback

Allows querying GPIO direction from the pad config register.
If the pad is not in GPIO mode, return an error.

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