gpiolib: assign chip owner to dev->driver->owner if not set

Assign GPIO chip owner field to chip->dev->driver->owner if it was not
configured by GPIO driver.

Cc: Johan Hovold <johan@kernel.org>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>