If we wait until the GPIO device's .release() callback gets invoked
before we remove it from the global device list, then we risk that
someone will look it up using gpio_device_find() between where we
dropped the last reference and before .release() is done taking a
reference again to an object that's being released.

The device must be removed when it's being unregistered - just like how
we remove it from the GPIO bus.

Fixes: ff2b1359 ("gpio: make the gpiochip a real device")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>