Bluetooth: Add Recv RR (P=0)(F=0) for SREJ_SENT state on ERTM

This finishes the implementation of Recv RR (P=0)(F=0) for the Enhanced
Retransmission Mode on L2CAP.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/l2cap.c

@@ -3517,7 +3517,10 @@ static inline int l2cap_data_channel_sframe(struct sock *sk, u16 rx_control, str
 				__mod_retrans_timer();
 
 			pi->conn_state &= ~L2CAP_CONN_REMOTE_BUSY;
-			l2cap_ertm_send(sk);
+			if (pi->conn_state & L2CAP_CONN_SREJ_SENT)
+				l2cap_send_ack(pi);
+			else
+				l2cap_ertm_send(sk);
 		}
 		break;