ll_temac: Reset dma descriptors indexes on ndo_open

The dma descriptors indexes are only initialized on the probe function.

If a packet is on the buffer when temac_stop is called, the dma
descriptors indexes can be left on a incorrect state where no other
package can be sent.

So an interface could be left in an usable state after ifdow/ifup.

This patch makes sure that the descriptors indexes are in a proper
status when the device is open.

Signed-off-by: Ricardo Ribalda Delgado <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/xilinx/ll_temac_main.c

···
 		       lp->rx_bd_p + (sizeof(*lp->rx_bd_v) * (RX_BD_NUM - 1)));
 	lp->dma_out(lp, TX_CURDESC_PTR, lp->tx_bd_p);
 
+	/* Init descriptor indexes */
+	lp->tx_bd_ci = 0;
+	lp->tx_bd_next = 0;
+	lp->tx_bd_tail = 0;
+	lp->rx_bd_ci = 0;
+
 	return 0;
 
 out: