[Bluetooth] Revert session reference counting fix

The fix for the reference counting problem of the signal DLC introduced
a race condition which leads to an oops. The reason for it is not fully
understood by now and so revert this fix, because the reference counting
problem is not crashing the RFCOMM layer and its appearance it rare.

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

net/bluetooth/rfcomm/core.c

···
 		rfcomm_dlc_unlock(d);
 
 		skb_queue_purge(&d->tx_queue);
-		rfcomm_session_put(s);
-
 		rfcomm_dlc_unlink(d);
 	}
 
···
 		*err = -ENOMEM;
 		goto failed;
 	}
-
-	rfcomm_session_hold(s);
 
 	s->initiator = 1;