bsc: Create a osmo_bsc_data and embed osmo_msc_data

We want to have multiple MSCs but we also have some data
that is only present on a per BSC basis. Right now the
MSC data is not allocated with talloc, so we have some
change in the talloc contexts.
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_msc.c b/openbsc/src/osmo-bsc/osmo_bsc_msc.c
index 04cfb99..a9da589 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_msc.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_msc.c
@@ -431,7 +431,7 @@
 
 int osmo_bsc_msc_init(struct gsm_network *network)
 {
-	struct osmo_msc_data *data = network->msc_data;
+	struct osmo_msc_data *data = &network->bsc_data->msc;
 
 	if (mgcp_create_port(data) != 0)
 		return -1;