BSSMAP_Emulation: use BSSAP_CodecPort

So far, BSSMAP_Emulation used the SCCPasp_SP_PORT directly, explicitly
calling BSSAP encode/decode functions while processing the primitives.

Let's clean this up and use the BSSAP_CodecPort which has meanwhile
been developed as a dual-faced port that can be stacked between SCCPasp
and the user to avoid any manual encode/decode function calls.

Change-Id: Icded789d18f3469f74e16f552df2c7ac44ac4294
diff --git a/bsc-nat/MSC_Simulation.ttcn b/bsc-nat/MSC_Simulation.ttcn
index f9fb0d4..7e39ca1 100755
--- a/bsc-nat/MSC_Simulation.ttcn
+++ b/bsc-nat/MSC_Simulation.ttcn
@@ -51,7 +51,7 @@
 	connect(vc_IPA:MTP3_SP_PORT, vc_SCCP:MTP3_SCCP_PORT);
 
 	/* connect BSSNAP dispatcher to upper side of SCCP */
-	connect(vc_BSSMAP:SCCP, vc_SCCP:SCCP_SP_PORT);
+	connect(vc_BSSMAP:BSSAP, vc_SCCP:SCCP_SP_PORT);
 
 	if (mp_mgcp_uses_udp == false) {
 		/* connect BSSMAP dispatcher to IPA_Emulation MGCP */