cosmetic: move mgcp_release_endp() to mgcp_ep.c

- move mgcp_release_endp() to mgcp_ep.c since it is clearly
  an endpoint sicific function.

Change-Id: I0a65b6e906c52a9e7cd75c88c4cbe1bf473b866b
diff --git a/src/libosmo-mgcp/mgcp_vty.c b/src/libosmo-mgcp/mgcp_vty.c
index 7043527..99780c8 100644
--- a/src/libosmo-mgcp/mgcp_vty.c
+++ b/src/libosmo-mgcp/mgcp_vty.c
@@ -27,6 +27,7 @@
 #include <osmocom/mgcp/mgcp_internal.h>
 #include <osmocom/mgcp/vty.h>
 #include <osmocom/mgcp/mgcp_conn.h>
+#include <osmocom/mgcp/mgcp_ep.h>
 
 #include <string.h>