gpio: use pinctrl device name for add range

gpiochip_add_pin_range() needs pinctrl device name as parameter.
Currently the parameter is pinctrl description name. So fix it.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>