pcu: Fix inadequate restriction on the referenced template parameter

Fixes:
 warning: Inadequate restriction on the referenced template parameter
 `chreq_desc', this may cause a dynamic test case error at runtime

Change-Id: I10b170c13aedc8abaaaf3b67d563ade8c3586c5b
diff --git a/pcu/GPRS_Components.ttcn b/pcu/GPRS_Components.ttcn
index bf2e868..3658fc8 100644
--- a/pcu/GPRS_Components.ttcn
+++ b/pcu/GPRS_Components.ttcn
@@ -423,7 +423,7 @@
 }
 
 function f_dltbf_ts_RLCMAC_DL_ACK_NACK(DlTbf dl_tbf, boolean use_egprs := false,
-				       template ChannelReqDescription chreq_desc := omit)
+				       template (omit) ChannelReqDescription chreq_desc := omit)
 runs on MS_BTS_IFACE_CT return template RlcmacUlBlock  {
 	if (use_egprs) {
 		return ts_RLCMAC_DL_ACK_NACK_EGPRS(dl_tbf.tfi, dl_tbf.egprs_acknack_desc, false, chreq_desc);