net/designware: Consecutive writes must have delay

This patch solves a TX/RX problem which happens at 10Mbps, due to the
fact that we are not respecting 4 cyles of the phy_clk (2.5MHz) between
two consecutive writes on the same register.

Signed-off-by: Armando Visconti <armando.visconti@st.com>
Signed-off-by: Amit Virdi <amit.virdi@st.com>

drivers/net/designware.c

@@ -175,8 +175,7 @@ static int dw_eth_init(struct eth_device *dev, bd_t *bis)
 	writel(readl(&dma_p->opmode) | RXSTART, &dma_p->opmode);
 	writel(readl(&dma_p->opmode) | TXSTART, &dma_p->opmode);
 
-	writel(readl(&mac_p->conf) | RXENABLE, &mac_p->conf);
-	writel(readl(&mac_p->conf) | TXENABLE, &mac_p->conf);
+	writel(readl(&mac_p->conf) | RXENABLE | TXENABLE, &mac_p->conf);
 
 	return 0;
 }