mgcp_ratectr: refactor rate counter and set group name

The rate counter group is currently only referenced by an index. In a
system with multiple trunks this makes it difficult to say which rate
counter group belongs to which trunk sinde the index that is used does
not necessarly corespond to a specific trunk.

Since rate counter groups can now get a human readable name assigned, we
should do that.

Also E1 specific rate counters only make sense for E1-trunks, so they
should not be present on the virtual trunk.

Change-Id: I5e7f0e9081a06af48e284afa5c36a095b2847704
diff --git a/include/osmocom/mgcp/mgcp_ratectr.h b/include/osmocom/mgcp/mgcp_ratectr.h
index 84315e0..78c687b 100644
--- a/include/osmocom/mgcp/mgcp_ratectr.h
+++ b/include/osmocom/mgcp/mgcp_ratectr.h
@@ -90,5 +90,8 @@
 	struct rate_ctr_group *e1_stats;
 };
 
-int mgcp_ratectr_global_alloc(void *ctx, struct mgcp_ratectr_global *ratectr);
-int mgcp_ratectr_trunk_alloc(void *ctx, struct mgcp_ratectr_trunk *ratectr);
+struct mgcp_config;
+struct mgcp_trunk;
+
+int mgcp_ratectr_global_alloc(struct mgcp_config *cfg);
+int mgcp_ratectr_trunk_alloc(struct mgcp_trunk *trunk);