osmo-mgw: rename struct mgcp_trunk_config and symbol tcfg

rename struct mgcp_trunk_config to struct mgcp_trunk and the related
symbol name "tcfg" to "trunk" in order to better match the reality.

Change-Id: I02889dbf8149e139b1bd0326e13ce4c1aec867d1
Related: OS#2659
diff --git a/include/osmocom/mgcp/mgcp_endp.h b/include/osmocom/mgcp/mgcp_endp.h
index 4c2caad..8fa8390 100644
--- a/include/osmocom/mgcp/mgcp_endp.h
+++ b/include/osmocom/mgcp/mgcp_endp.h
@@ -81,7 +81,7 @@
 	struct mgcp_config *cfg;
 
 	/*! Backpointer to the Trunk specific configuration */
-	struct mgcp_trunk_config *tcfg;
+	struct mgcp_trunk *trunk;
 
 	/*! Endpoint properties (see above) */
 	const struct mgcp_endpoint_type *type;
@@ -101,6 +101,6 @@
 };
 
 /*! Extract endpoint number for a given endpoint */
-#define ENDPOINT_NUMBER(endp) abs((int)(endp - endp->tcfg->endpoints))
+#define ENDPOINT_NUMBER(endp) abs((int)(endp - endp->trunk->endpoints))
 
 void mgcp_endp_release(struct mgcp_endpoint *endp);