PCUIF: rename tlli to msg_id

To confirm downlink IMMEDIATE ASSIGNMENT messages, we use the TLLI as an
identifier and the related record member is also called "tlli".
Unfortunately this is misleading since the message identifier does not
necessarly have to be a TLLI. It is just an implementation detail that
osmo-pcu uses the TLLI as a message identifier.

To make that clear, lets rename the tlli member (and variable and
parameter names where it is passed on) to "msg_id".

(Since this change only renames variables and struct members it will not
break compatibility with other programs that use the PCUIF)

Related: OS#5927
Depends: osmo-pcu.git I4a25039dfe329e68879bc68936e49c4b190625e6
Change-Id: I1db29d5b1920e351c452b798c3260654c2cbe0cb
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 1ab0f8a..e8ae1c0 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -5820,7 +5820,7 @@
 		f_pcu_data_req(0, 0, 0, 0, 0, PCU_IF_SAPI_PCH, '313233'O & c_PCU_DATA);
 	} else {
 		var PCUIF_pch_dt pch_dt;
-		pch_dt.tlli := '01020304'O;
+		pch_dt.msg_id := '01020304'O;
 		pch_dt.imsi := "00101000000000123";
 		pch_dt.data := c_PCU_DATA;
 		f_pcu_data_req(0, 0, 0, 0, 0, PCU_IF_SAPI_PCH_DT, enc_PCUIF_pch_dt(pch_dt));