PCU: s/f_establish_tbf/f_pcuif_tx_rach_rx_imm_ass/g

Fix confusion: f_ms_establish_ul_tbf() vs f_establish_tbf(). The
new name precisely describes what the function does. Sending a
RACH.ind and receiving a DATA.req with RR Immediate Assignment
is just a part of the TBF establishment process.

Change-Id: I1e22b9936bf68ebcaf70cefbc57345995ebbbaed
diff --git a/pcu/PCU_Tests.ttcn b/pcu/PCU_Tests.ttcn
index 5fb4b2b..bdcf7c1 100644
--- a/pcu/PCU_Tests.ttcn
+++ b/pcu/PCU_Tests.ttcn
@@ -1518,7 +1518,7 @@
 	ra11 := enc_EGPRSPktChRequest2uint(req);
 	log("Sending EGPRS Packet Channel Request (", ra11, "): ", req);
 
-	rr_msg := f_establish_tbf(ra := ra11, is_11bit := 1, burst_type := bt);
+	rr_msg := f_pcuif_tx_rach_rx_imm_ass(ra := ra11, is_11bit := 1, burst_type := bt);
 	if (not match(rr_msg, t_imm_ass)) {
 		setverdict(fail, "Immediate Assignment does not match");
 		f_shutdown(__BFILE__, __LINE__);