[codecs filter] store BSS codec list from Compl L3

The initial Compl L3 happens long before we establish a CC transaction.
Remember the Codec List (BSS Supported), so that we can feed the new
codecs filter with it. Subsequent patches implement feeding the filter.

Related: SYS#5066
Change-Id: I7cdc348218433141a43d2e42750af02591688240
diff --git a/include/osmocom/msc/msc_a.h b/include/osmocom/msc/msc_a.h
index e56ea52..18eb76c 100644
--- a/include/osmocom/msc/msc_a.h
+++ b/include/osmocom/msc/msc_a.h
@@ -121,6 +121,9 @@
 	 *                   \-------RTP--> (ISUP) <--RTP--> <--RTP-->
 	 */
 	struct {
+		/* Codec List (BSS Supported) as received during Complete Layer 3 Information */
+		struct gsm0808_speech_codec_list compl_l3_codec_list_bss_supported;
+
 		/* All of the RTP stream handling */
 		struct call_leg *call_leg;
 		struct mncc_call *mncc_forwarding_to_remote_ran;