in ran_msg, return gsm0808_speech_codec (intra-MSC)

Do not convert to enum mgcp_codecs, but directly pass the
gsm0808_speech_codec IE from the A interface to codecs handling.

For Iu:
- RAN side: use ran_infra.force_mgw_codecs_to_ran to keep the MGW
  endpoint towards RAN on IUFP.
- CN side: introduce flag ran_msg.assignment_complete.codec_with_iuup,
  so to decide whether to forward IUFP towards CN, we don't need to test
  the RAN type, but use the flag from the ran_msg implementation.

In msc_vlr_tests, use the SDP codec string instead of enum
mgcp_codecs.

So far limit to intra-MSC related messaging, adjusting inter-MSC
handover follows in a separate patch.

Change-Id: Ia666cb697fbd140d7239089628faed93860ce671
diff --git a/tests/msc_vlr/msc_vlr_tests.h b/tests/msc_vlr/msc_vlr_tests.h
index 1f83013..1a57101 100644
--- a/tests/msc_vlr/msc_vlr_tests.h
+++ b/tests/msc_vlr/msc_vlr_tests.h
@@ -186,7 +186,7 @@
 void ms_sends_classmark_update(const struct osmo_gsm48_classmark *classmark);
 void ms_sends_ciphering_mode_complete(const char *inner_nas_msg);
 void ms_sends_security_mode_complete(uint8_t utran_encryption);
-void ms_sends_assignment_complete(enum mgcp_codecs assigned_codec);
+void ms_sends_assignment_complete(const char *sdp_codec_name);
 void gsup_rx(const char *rx_hex, const char *expect_tx_hex);
 void send_sms(struct vlr_subscr *receiver,
 	      struct vlr_subscr *sender,