6lowpan_rtnl: fix off by one while fragmentation

This patch fix a off by one error while fragmentation. If the frag_cap
value is equal to skb_unprocessed value we need to stop the
fragmentation loop because the last fragment which has a size of
skb_unprocessed fits into the frag capability size.

This issue was introduced by commit d4b2816d
("6lowpan: fix fragmentation").
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan_rtnl.c

@@ -328,7 +328,7 @@ lowpan_xmit_fragmented(struct sk_buff *skb, struct net_device *dev,
 				 __func__, frag_tag, skb_offset);
 			goto err;
 		}
-	} while (skb_unprocessed >= frag_cap);
+	} while (skb_unprocessed > frag_cap);
 
 	consume_skb(skb);
 	return NET_XMIT_SUCCESS;