iio: dac: ad5592r: destroy mutexes in detach paths

The locks used here are initialized but never released which causes
resource leaks with mutex debugging enabled. Add missing calls to
mutex_destroy() or use devres if applicable.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250409-gpiochip-set-rv-iio-v2-1-4b36428f39cb@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/ad5592r-base.c

@@ -155,6 +155,8 @@ static void ad5592r_gpio_cleanup(struct ad5592r_state *st)
 {
 	if (st->gpio_map)
 		gpiochip_remove(&st->gpiochip);
+
+	mutex_destroy(&st->gpio_lock);
 }
 
 static int ad5592r_reset(struct ad5592r_state *st)
@@ -606,6 +608,10 @@ int ad5592r_probe(struct device *dev, const char *name,
 	st->num_channels = 8;
 	dev_set_drvdata(dev, iio_dev);
 
+	ret = devm_mutex_init(dev, &st->lock);
+	if (ret)
+		return ret;
+
 	st->reg = devm_regulator_get_optional(dev, "vref");
 	if (IS_ERR(st->reg)) {
 		if ((PTR_ERR(st->reg) != -ENODEV) && dev_fwnode(dev))
@@ -622,8 +628,6 @@ int ad5592r_probe(struct device *dev, const char *name,
 	iio_dev->info = &ad5592r_info;
 	iio_dev->modes = INDIO_DIRECT_MODE;
 
-	mutex_init(&st->lock);
-
 	ad5592r_init_scales(st, ad5592r_get_vref(st));
 
 	ret = ad5592r_reset(st);