gpio: zevio: Use proper headers and drop OF_GPIO dependency

The driver doesn't depend on the OF_GPIO to be compiled. Hence
the proper header to use is mod_devicetable.h. Replace of*.h with
the above mentioned and drop redundant dependency.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>