Delay ImmAss(PCH, PktDlAss) if waiting for PKT_CTRL_ACK answering UL_ACK_NACK (FinACK=1)

In that state (ul_tbf=TBF_ST_FINISHED), we are unable to reach the MS to
assign a new DL TBF.
* MS Is not available in CCCH because it's attached the PDCH.
* MS won't be able to PKT_CTRL_ACK a PktDlAss on PACCH, because next
  thing it will do is to PKT_CTRL_ACK the UL_ACK_NACK(FINACK=1) we
  already polled it for, and immediatelly after that it will release the
  UL TBF on its side and go back to packet idle mode.

Hence, we must wait for MS to send the PKT_CTRL_ACK to us in order to be
able to assign the DL TBF in PCH (CCCH).

Related: OS#5700
Change-Id: I7a30db9cc7dae70e04054f1a4dba004bd1780d4a
diff --git a/src/tbf_fsm.h b/src/tbf_fsm.h
index 9814c0e..22266e7 100644
--- a/src/tbf_fsm.h
+++ b/src/tbf_fsm.h
@@ -32,7 +32,7 @@
 	TBF_EV_LAST_DL_DATA_SENT, /* DL TBF sends RLCMAC block containing last DL avilable data buffered */
 	TBF_EV_LAST_UL_DATA_RECVD, /* UL TBF sends RLCMAC block containing last UL data (cv=0) */
 	TBF_EV_FINAL_ACK_RECVD, /* DL ACK/NACK with FINAL_ACK=1 received from MS */
-	TBF_EV_FINAL_UL_ACK_CONFIRMED, /* UL TBF: MS ACKs (CtrlAck or PktResReq) our UL ACK/NACK w/ FinalAckInd=1 */
+	TBF_EV_FINAL_UL_ACK_CONFIRMED, /* UL TBF: MS ACKs (CtrlAck or PktResReq) our UL ACK/NACK w/ FinalAckInd=1. data = (bool) MS requests establishment of a new UL-TBF. */
 	TBF_EV_MAX_N3101, /* MAX N3101 (max usf timeout) reached (UL TBF) */
 	TBF_EV_MAX_N3103, /* MAX N3103 (max Pkt Ctrl Ack for last UL ACK/NACK timeout) reached (UL TBF) */
 	TBF_EV_MAX_N3105, /* MAX N3105 (max poll timeout) reached (UL/DL TBF) */