net/designware: ensure device private data is DMA aligned.

struct dw_eth_dev contains fields which are accessed via DMA, so make sure it
is aligned to a dma boundary. Without this I see:
    ERROR: v7_dcache_inval_range - start address is not aligned - 0x7fb677e0

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
Acked-by: Marek Vasut <marex@denx.de>

drivers/net/designware.c

@@ -414,7 +414,8 @@ int designware_initialize(ulong base_addr, u32 interface)
 	 * Since the priv structure contains the descriptors which need a strict
 	 * buswidth alignment, memalign is used to allocate memory
 	 */
-	priv = (struct dw_eth_dev *) memalign(16, sizeof(struct dw_eth_dev));
+	priv = (struct dw_eth_dev *) memalign(ARCH_DMA_MINALIGN,
+					      sizeof(struct dw_eth_dev));
 	if (!priv) {
 		free(dev);
 		return -ENOMEM;