gpio: rdc321x: Prevent removal of modules exporting active GPIOs

This driver can be built as a module, set the missing owner field of
struct gpio_chip to prevent removal of modules exporting active GPIOs.

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