gpiolib: use a more explicit retval logic in gpiochip_get_direction()

gpiolib: use a more explicit retval logic in gpiochip_get_direction()

We have existing macros for direction settings so we don't need to rely
on the magic value of 1 in the retval check. Use readable logic that
explicitly says we expect INPUT, OUTPUT or a negative errno and nothing
else in gpiochip_get_direction().

Fixes: e623c4303ed1 ("gpiolib: sanitize the return value of gpio_chip::get_direction()")
Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Closes: https://lore.kernel.org/all/Z7yfTggRrk3K6srs@black.fi.intel.com/
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250226-retval-fixes-v2-2-c8dc57182441@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>