crypto: ixp4xx - dma_unmap the correct address

Testing ixp4xx_crypto with CONFIG_DMA_API_DEBUG lead to the following error:
DMA-API: platform ixp4xx_crypto.0: device driver tries to free DMA memory it has not allocated [device address=0x0000000000000000] [size=24 bytes]

This is due to dma_unmap using the wrong address.

Fixes: 0d44dc59 ("crypto: ixp4xx - Fix handling of chained sg buffers")
Signed-off-by: NCorentin Labbe <clabbe@baylibre.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/ixp4xx_crypto.c

@@ -330,7 +330,7 @@ static void free_buf_chain(struct device *dev, struct buffer_desc *buf,
 
 		buf1 = buf->next;
 		phys1 = buf->phys_next;
-		dma_unmap_single(dev, buf->phys_next, buf->buf_len, buf->dir);
+		dma_unmap_single(dev, buf->phys_addr, buf->buf_len, buf->dir);
 		dma_pool_free(buffer_pool, buf, phys);
 		buf = buf1;
 		phys = phys1;