Pinctrl: Ingenic: Unify the function name prefix to "ingenic_gpio_".

In the original code, some function names begin with "ingenic_gpio_",
and some with "gpio_ingenic_". For the sake of uniform style,
all of them are changed to the beginning of "ingenic_gpio_".

Signed-off-by: Zhou Yanjie <zhouyanjie@cduestc.edu.cn>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>