reset: gpio: add the "compatible" property

reset: gpio: add the "compatible" property

In order to correctly handle the interaction between the reset-gpio
devices and shared GPIOs managed by GPIOLIB, we need to be able to
identify the former. Add the "compatible" property to allow us to use
the device_is_compatible() helper.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>