ntb_netdev: fix sleep time mismatch

The tx_time should be in usecs (according to the comment above the
variable), but the setting of the timer during the rearming is done in
msecs.  Change it to match the expected units.

Fixes: e74bfeedad08 ("NTB: Add flow control to the ntb_netdev")
Suggested-by: Gerd W. Haeussler <gerd.haeussler@cesys-it.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Acked-by: Dave Jiang <dave.jiang@intel.com>

drivers/net/ntb_netdev.c

@@ -236,7 +236,7 @@ static void ntb_netdev_tx_timer(struct timer_list *t)
 	struct net_device *ndev = dev->ndev;
 
 	if (ntb_transport_tx_free_entry(dev->qp) < tx_stop) {
-		mod_timer(&dev->tx_timer, jiffies + msecs_to_jiffies(tx_time));
+		mod_timer(&dev->tx_timer, jiffies + usecs_to_jiffies(tx_time));
 	} else {
 		/* Make sure anybody stopping the queue after this sees the new
 		 * value of ntb_transport_tx_free_entry()