mgcp_codec_add: fix audio_name size check

Needs to account for terminating '\0'.

Change-Id: I27896beef6ffcc1cb6207daaba6c8b2b03eb513d
diff --git a/src/libosmo-mgcp/mgcp_codec.c b/src/libosmo-mgcp/mgcp_codec.c
index 704b7e6..9e55ab0 100644
--- a/src/libosmo-mgcp/mgcp_codec.c
+++ b/src/libosmo-mgcp/mgcp_codec.c
@@ -179,7 +179,7 @@
 	/* Now we extract the codec subtype name, rate and channels. The latter
 	 * two are optional. If they are not present we use the safe defaults
 	 * above. */
-	if (strlen(audio_name) > sizeof(audio_codec)) {
+	if (strlen(audio_name) >= sizeof(audio_codec)) {
 		LOGP(DLMGCP, LOGL_ERROR, "Audio codec too long: %s\n", osmo_quote_str(audio_name, -1));
 		goto error;
 	}