don't include hnbgw.h from ranap header files

To use libosmo-ranap from outside of this repository, we need to
eliminated all dependencies to local header files
diff --git a/src/hnbgw.c b/src/hnbgw.c
index ea3e754..b3d1b63 100644
--- a/src/hnbgw.c
+++ b/src/hnbgw.c
@@ -434,6 +434,7 @@
 	}
 
 	osmo_sua_set_log_area(DSUA);
+	ranap_set_log_area(DRANAP);
 
 	g_hnb_gw->cnlink_cs = hnbgw_cnlink_init(g_hnb_gw, "127.0.0.1", SUA_PORT);
 	g_hnb_gw->cnlink_ps = hnbgw_cnlink_init(g_hnb_gw, "127.0.0.2", SUA_PORT);