iio: buffer-dmaengine: fix releasing dma channel on error

If dma_get_slave_caps() fails, we need to release the dma channel before
returning an error to avoid leaking the channel.

Fixes: 2d6ca60 ("iio: Add a DMAengine framework based buffer")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240723-iio-fix-dmaengine-free-on-error-v1-1-2c7cbc9b92ff@baylibre.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/buffer/industrialio-buffer-dmaengine.c

@@ -237,7 +237,7 @@ static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 
 	ret = dma_get_slave_caps(chan, &caps);
 	if (ret < 0)
-		goto err_free;
+		goto err_release;
 
 	/* Needs to be aligned to the maximum of the minimums */
 	if (caps.src_addr_widths)
@@ -263,6 +263,8 @@ static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
 
 	return &dmaengine_buffer->queue.buffer;
 
+err_release:
+	dma_release_channel(chan);
 err_free:
 	kfree(dmaengine_buffer);
 	return ERR_PTR(ret);