Move gprs_gb_parse.[c,h] to tests/sgsn/

That big file is really only used by tests/sgsn/sgsn_test nowadays, so
let's keep it out of osmo-sgsn app code base.

Change-Id: Ia5a639832f52b2f015a2800bd0d94a28d7bc689b
diff --git a/tests/sgsn/sgsn_test.c b/tests/sgsn/sgsn_test.c
index 2c41e8e..a09f1a5 100644
--- a/tests/sgsn/sgsn_test.c
+++ b/tests/sgsn/sgsn_test.c
@@ -27,7 +27,6 @@
 #include <osmocom/gsm/gsup.h>
 #include <osmocom/gsupclient/gsup_client.h>
 #include <osmocom/sgsn/gprs_utils.h>
-#include <osmocom/sgsn/gprs_gb_parse.h>
 #include <osmocom/sgsn/gprs_gmm_fsm.h>
 
 #include <osmocom/gprs/gprs_bssgp.h>
@@ -42,6 +41,8 @@
 
 #include <stdio.h>
 
+#include "gprs_gb_parse.h"
+
 void *tall_sgsn_ctx;
 static struct sgsn_instance sgsn_inst = {
 	.config_file = "osmo_sgsn.cfg",