PCU_Tests_RAW.ttcn: add test case for UL link quality adaptation

This change introduces a new test case TC_cs_lqual_ul_tbf, which
is aimed to test the feedback of OsmoPCU on changing link quality
measurements in Uplink Data blocks during an active TBF.

Change-Id: Ia78d93e43a3c41b0b30e70df20a2da31077fd05f
Related: SYS#4607
diff --git a/library/RLCMAC_Types.ttcn b/library/RLCMAC_Types.ttcn
index f3deafc..39c0c97 100644
--- a/library/RLCMAC_Types.ttcn
+++ b/library/RLCMAC_Types.ttcn
@@ -312,7 +312,7 @@
 			mac_hdr := {
 				payload_type := (MAC_PT_RLCMAC_NO_OPT, MAC_PT_RLCMAC_OPT),
 				rrbp:= ?,
-				rrbp_valid := true,
+				rrbp_valid := ?,
 				usf := ?
 			},
 			opt := *,