net: fix network drivers ndo_start_xmit() return values (part 2)

Fix up IRDA drivers that return an errno value to qdisc_restart(), causing
qdisc_restart() to print a warning an requeue/retransmit the skb.

- donauboe: intention appears to be to have the skb retransmitted without
            error message
- irda-usb: intention is to drop silently according to comment
- kingsub-sir: skb is freed: use after free
- ks959-sir: skb is freed: use after free
- ksdazzle-sir: skb is freed: use after free
- mcs7880: skb is freed: use after free

All but donauboe compile tested.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/irda/donauboe.c b/drivers/net/irda/donauboe.c
index 6b6548b..9a0346e 100644
--- a/drivers/net/irda/donauboe.c
+++ b/drivers/net/irda/donauboe.c
@@ -994,11 +994,11 @@
 
   /* change speed pending, wait for its execution */
   if (self->new_speed)
-      return -EBUSY;
+      return NETDEV_TX_BUSY;
 
   /* device stopped (apm) wait for restart */
   if (self->stopped)
-      return -EBUSY;
+      return NETDEV_TX_BUSY;
 
   toshoboe_checkstuck (self);
 
@@ -1049,7 +1049,7 @@
       if (self->txpending)
         {
 	  spin_unlock_irqrestore(&self->spinlock, flags);
-          return -EBUSY;
+          return NETDEV_TX_BUSY;
         }
 
       /* If in SIR mode we need to generate a string of XBOFs */
@@ -1105,7 +1105,7 @@
           ,skb->len, self->ring->tx[self->txs].control, self->txpending);
       toshoboe_start_DMA(self, OBOE_CONFIG0H_ENTX);
       spin_unlock_irqrestore(&self->spinlock, flags);
-      return -EBUSY;
+      return NETDEV_TX_BUSY;
     }
 
   if (INB (OBOE_ENABLEH) & OBOE_ENABLEH_SIRON)