gpio: zevio: Remove of_match_ptr around zevio_gpio_of_match

This is a DT-only driver and it will be built only when CONFIG_OF is set.
So it's pointless to use of_match_ptr.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>