mgcp: Rename TOS to DSCP

DSCP is the more modern information for TOS and the kernel
will set parts of TOS by itself (e.g. for ECN).
diff --git a/openbsc/src/mgcp/mgcp_network.c b/openbsc/src/mgcp/mgcp_network.c
index 8b41227..6e6b7a6 100644
--- a/openbsc/src/mgcp/mgcp_network.c
+++ b/openbsc/src/mgcp/mgcp_network.c
@@ -255,8 +255,8 @@
 		goto cleanup1;
 	}
 
-	set_ip_tos(endp->local_rtp.fd, cfg->endp_tos);
-	set_ip_tos(endp->local_rtcp.fd, cfg->endp_tos);
+	set_ip_tos(endp->local_rtp.fd, cfg->endp_dscp);
+	set_ip_tos(endp->local_rtcp.fd, cfg->endp_dscp);
 
 	endp->local_rtp.cb = rtp_data_cb;
 	endp->local_rtp.data = endp;