gpio: Fix dependency for gpio-delay

This driver relies on OF_GPIO features, add a dependency to Kconfig.

Fixes: cf5dec80 ("gpio: Add gpio delay driver")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>