BTS_Tests: fix CHANnel ACTIVation message in TC_meas_res_sign_tchX

The testcase TC_meas_res_sign_tchX activates a traffic channel in
signalling mode and checks the RSL resulting measurement reports.

The CHANnel ACTIVation message sets "SDCCH" as "Channel rate and Type"
value. This is invalid, the "Channel Rate and Type" sould be set to "Half /
Full rate TCH Channel Lm / Bm" (while the speech or data indicator is
still set to "Signalling")

Change-Id: I51887b0d0379fcc1f4483d08dfdd6869e7a9f963
Related: OS#4799
diff --git a/library/RSL_Types.ttcn b/library/RSL_Types.ttcn
index 05effa2..ff60a37 100644
--- a/library/RSL_Types.ttcn
+++ b/library/RSL_Types.ttcn
@@ -397,13 +397,14 @@
 		RSL_SpeechAlgo	coding_alg_rate
 	} with { variant (len) "LENGTHTO(reserved,dtx_d,dtx_u,spd_ind,ch_rate_type,coding_alg_rate)" }
 
-	template (value) RSL_IE_ChannelMode ts_RSL_ChanMode_SIGN(boolean dtx_downlink := false) := {
+	template (value) RSL_IE_ChannelMode ts_RSL_ChanMode_SIGN(boolean dtx_downlink := false,
+								 RSL_ChanRateType t := RSL_CHRT_SDCCH) := {
 		len := 0,	/* overwritten */
 		reserved := '000000'B,
 		dtx_d := dtx_downlink,
 		dtx_u := false,
 		spd_ind := RSL_SPDI_SIGN,
-		ch_rate_type := RSL_CHRT_SDCCH,
+		ch_rate_type := t,
 		coding_alg_rate := RSL_CMOD_NO_RESOURCE
 	}