gpio: remove unnecessary checks from gpiod_to_chip()

We don't need to check the gdev pointer in struct gpio_desc - it's
always assigned and never cleared. It's also pointless to check
gdev->chip before we actually serialize access to it.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>