gpio: zevio: drop of_gpio.h header

Remove of_gpio.h header file, replace of_* functions and structs
with appropriate alternatives.

Signed-off-by: Moses Christopher Bollavarapu <mosescb.dev@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>