mgcp: Honor the rtp IP_TOS settings for Osmux

Honor the IP_TOS settings for Osmux as well. Re-use the RTP
setting as it makes sense to classify the audio packets the
same way.

Fixes: OW#1369
diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index 37fc59a..c3f43dd 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -901,7 +901,7 @@
 	return 0;
 }
 
-static int set_ip_tos(int fd, int tos)
+int mgcp_set_ip_tos(int fd, int tos)
 {
 	int ret;
 	ret = setsockopt(fd, IPPROTO_IP, IP_TOS,
@@ -925,8 +925,8 @@
 		goto cleanup1;
 	}
 
-	set_ip_tos(rtp_end->rtp.fd, cfg->endp_dscp);
-	set_ip_tos(rtp_end->rtcp.fd, cfg->endp_dscp);
+	mgcp_set_ip_tos(rtp_end->rtp.fd, cfg->endp_dscp);
+	mgcp_set_ip_tos(rtp_end->rtcp.fd, cfg->endp_dscp);
 
 	rtp_end->rtp.when = BSC_FD_READ;
 	if (osmo_fd_register(&rtp_end->rtp) != 0) {