Unduplicate the offset check by simply calling gpiochip_get_desc() and
checking its return value.
Signed-off-by: NBartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>