stmmac: fix Transmit FIFO flush operation

Fix the Transmit FIFO flush operation; it was
disabled while reworking the descriptor structures.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/stmmac/dwmac_lib.c b/drivers/net/stmmac/dwmac_lib.c
index d4adb1e..0a504ad 100644
--- a/drivers/net/stmmac/dwmac_lib.c
+++ b/drivers/net/stmmac/dwmac_lib.c
@@ -227,6 +227,13 @@
 	return ret;
 }
 
+void dwmac_dma_flush_tx_fifo(unsigned long ioaddr)
+{
+	u32 csr6 = readl(ioaddr + DMA_CONTROL);
+	writel((csr6 | DMA_CONTROL_FTF), ioaddr + DMA_CONTROL);
+
+	do {} while ((readl(ioaddr + DMA_CONTROL) & DMA_CONTROL_FTF));
+}
 
 void stmmac_set_mac_addr(unsigned long ioaddr, u8 addr[6],
 			 unsigned int high, unsigned int low)