mgcp_internal: remove forward declaration struct mgcp_endpoint_type

In is no longer needed to define struct mgcp_endpoint_type in
mgcp_internal.h

Change-Id: Iecea75e5620e8a2f1fd2066949c116bf72320aca
Related: OS#2659
diff --git a/include/osmocom/mgcp/mgcp_internal.h b/include/osmocom/mgcp/mgcp_internal.h
index a9d5ea4..ec3ce31 100644
--- a/include/osmocom/mgcp/mgcp_internal.h
+++ b/include/osmocom/mgcp/mgcp_internal.h
@@ -197,12 +197,6 @@
 
 #include <osmocom/mgcp/mgcp_conn.h>
 
-struct mgcp_endpoint_type;
-
-
-
-
-
 /**
  * Internal structure while parsing a request
  */