Bluetooth: Add L2CAP channel to skb private data

Adding the channel to the skb private data makes possible to us know which
channel the skb we have came from.

Signed-off-by: Gustavo Padovan <[e-mail]
Signed-off-by: Marcel Holtmann <[e-mail]>

include/net/bluetooth/bluetooth.h

···
 	__u8 incoming;
 	__u16 expect;
 	__u8 force_active;
+	struct l2cap_chan *chan;
 	struct l2cap_ctrl control;
 	struct hci_req_ctrl req;
 	bdaddr_t bdaddr;

net/bluetooth/l2cap_sock.c

···
 	if (!skb)
 		return ERR_PTR(err);
 
+	bt_cb(skb)->chan = chan;
+
 	return skb;
 }