Bluetooth: 6lowpan: Print errors during recv_pkt

This makes should make it more clear why a packet is being dropped.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/6lowpan.c

@@ -337,6 +337,7 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 
 		ret = iphc_decompress(local_skb, dev, peer);
 		if (ret < 0) {
+			BT_DBG("iphc_decompress failed: %d", ret);
 			kfree_skb(local_skb);
 			goto drop;
 		}
@@ -356,6 +357,7 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 		consume_skb(local_skb);
 		consume_skb(skb);
 	} else {
+		BT_DBG("unknown packet type");
 		goto drop;
 	}