sdp_msg: s/sdp_audio_codec_/sdp_audio_codecs_

Some functions act on a struct sdp_audio_codecs but begin with the name
sdp_audio_codec (singular). That's confusing.

Related: SYS#5066
Change-Id: Id87eb350c1f17f8dbf776909824bfa06634c1d04
diff --git a/tests/sdp_msg/sdp_msg_test.c b/tests/sdp_msg/sdp_msg_test.c
index e891953..ee48e80 100644
--- a/tests/sdp_msg/sdp_msg_test.c
+++ b/tests/sdp_msg/sdp_msg_test.c
@@ -531,7 +531,7 @@
 			break;
 		}
 		printf("SDP: %s\n", sdp_audio_codecs_to_str(&sdp.audio_codecs));
-		codec = sdp_audio_codec_by_payload_type(&sdp.audio_codecs, t->select_payload_type, false);
+		codec = sdp_audio_codecs_by_payload_type(&sdp.audio_codecs, t->select_payload_type, false);
 		OSMO_ASSERT(codec);
 		printf("Select: %s\n", sdp_audio_codec_to_str(codec));