pinctrl: ocelot: Always register GPIO driver

pinctrl: ocelot: Always register GPIO driver

[ Upstream commit 550713e33f4338c8596776828a936fd1e3bf35de ]

This fixes the situation where the GPIO controller is not
used as an interrupt controller as well.

Previously, the driver would silently fail to register even the
GPIO's. With this change, the driver will only register as an
interrupt controller if a parent interrupt is provided.

Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Link: https://lore.kernel.org/r/20200513125532.24585-2-lars.povlsen@microchip.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>