bts/BTS_Tests: cosmetic: use mp_trx0_arfcn in ts_ChanDescH0

Change-Id: I07a91b6517d2f19e127d36d79e6d2136bd2c29bb
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index f20a29b..6811e38 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -3158,7 +3158,7 @@
 }
 
 template (value) ChannelDescription ts_ChanDescH0(template (value) RslChannelNr chan_nr, uint3_t tsc := 7,
-						  uint12_t arfcn := 871) := {
+						  uint12_t arfcn := mp_trx0_arfcn) := {
 	chan_nr := chan_nr,
 	tsc := tsc,
 	h := false,