osmux: Attach osmux to virtual trunk

It makes sense to handle one osmux socket per trunk. Since we only so
far operate one RTP/osmux trunk, let's stick to that only one for
simplicity.

Change-Id: I173266c4058d5db9479d773d7dec1304bc8f1f99
diff --git a/src/libosmo-mgcp/mgcp_protocol.c b/src/libosmo-mgcp/mgcp_protocol.c
index a9e8818..74ed871 100644
--- a/src/libosmo-mgcp/mgcp_protocol.c
+++ b/src/libosmo-mgcp/mgcp_protocol.c
@@ -741,7 +741,7 @@
 static int mgcp_osmux_setup(struct mgcp_endpoint *endp, const char *line)
 {
 	if (!endp->trunk->cfg->osmux_init) {
-		if (osmux_init(OSMUX_ROLE_BSC, endp->trunk->cfg) < 0) {
+		if (osmux_init(OSMUX_ROLE_BSC, endp->trunk) < 0) {
 			LOGPENDP(endp, DLMGCP, LOGL_ERROR, "Cannot init OSMUX\n");
 			return -3;
 		}