gpio: sysfs: call mutex_destroy() in gpiod_unexport()

While not critical, it's useful to have the corresponding call to
mutex_destroy() whenever we use mutex_init(). Add the call right before
kfreeing the GPIO data.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250610-gpio-sysfs-chip-export-v1-3-a8c7aa4478b1@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpiolib-sysfs.c

@@ -713,6 +713,7 @@ void gpiod_unexport(struct gpio_desc *desc)
 	}
 
 	put_device(dev);
+	mutex_destroy(&data->mutex);
 	kfree(data);
 }
 EXPORT_SYMBOL_GPL(gpiod_unexport);