mgcp_network: improve coment

the comment that explains the AMR frame format check is a bit difficult
to understand, lets rephrase it.

Change-Id: I07f12c03449e1e8eda8bdd3edad6d1007f5ba48d

src/libosmo-mgcp/mgcp_network.c

@@ -1537,12 +1537,11 @@ static int rx_rtp(struct msgb *msg)
 	if (!trunk->rtp_accept_all && check_rtp_origin(conn_src, from_addr))
 		return -1;
 
-	/* If AMR is configured for the ingress connection and conversion of the
-	 * framing mode (octet-aligned vs. bandwith-efficient) is explicitly
-	 * defined, then we check if the incoming payload matches that
-	 * expectation. */
+	/* Handle AMR frame format conversion (octet-aligned vs. bandwith-efficient) */
 	if (mc->proto == MGCP_PROTO_RTP &&
 	    mgcp_codec_amr_align_mode_is_indicated(conn_src->end.codec)) {
+		/* Make sure that the incoming AMR frame format matches the frame format that the call agent has
+		 * communicated via SDP when the connection was created/modfied. */
 		int oa = amr_oa_check((char*)msgb_data(msg), msgb_length(msg));
 		if (oa < 0)
 			return -1;