dnet: enable transmit time stamping.

This patch enables software (and phy device) transmit time stamping
in the "Dave ethernet interface." Compile tested only.

Cc: Ilya Yanok <[e-mail]>
Signed-off-by: Richard Cochran <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/dnet.c

···
 		dnet_writel(bp, irq_enable, INTR_ENB);
 	}
 
+	skb_tx_timestamp(skb);
+
 	/* free the buffer */
 	dev_kfree_skb(skb);