gpio: sysfs: fix inverted pointer logic

The logic is inverted, we want to return if the chip *IS* NULL.

Fixes: d83cee3 ("gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-gpio/15671341-0b29-40e0-b487-0a4cdc414d8e@moroto.mountain/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: Bartosz Golaszewski

drivers/gpio/gpiolib-sysfs.c

@@ -802,7 +802,7 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 	guard(srcu)(&gdev->srcu);
 
 	chip = srcu_dereference(gdev->chip, &gdev->srcu);
-	if (chip)
+	if (!chip)
 		return;
 
 	/* unregister gpiod class devices owned by sysfs */