net: libwx: fix memory leak in wx_setup_rx_resources

When wx_alloc_page_pool() failed in wx_setup_rx_resources(), it doesn't
release DMA buffer. Add dma_free_coherent() in the error path to release
the DMA buffer.

Fixes: 850b971110b2 ("net: libwx: Allocate Rx and Tx resources")
Signed-off-by: Zhengchao Shao <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/wangxun/libwx/wx_lib.c

···
 	ret = wx_alloc_page_pool(rx_ring);
 	if (ret < 0) {
 		dev_err(rx_ring->dev, "Page pool creation failed: %d\n", ret);
-		goto err;
+		goto err_desc;
 	}
 
 	return 0;
+
+err_desc:
+	dma_free_coherent(dev, rx_ring->size, rx_ring->desc, rx_ring->dma);
 err:
 	kvfree(rx_ring->rx_buffer_info);
 	rx_ring->rx_buffer_info = NULL;