sgsn: Remove explicit sgsn_instance parameters

Currently the function in sgsn_auth.c either have an sgsn_config or
an sgsn_instance parameter. Since then global sgsn variable is
already being used in that file and since other parts of the SGSN
related code also rely on a global sgsn singleton, these parameters
pretend to provide a flexibility that is not really supported.

Therefore this patch removes these parameters except for the ACL
related functions, which do not call code that uses the sgsn
variable.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/sgsn_main.c b/openbsc/src/gprs/sgsn_main.c
index c7c852d..0310cb2 100644
--- a/openbsc/src/gprs/sgsn_main.c
+++ b/openbsc/src/gprs/sgsn_main.c
@@ -345,7 +345,7 @@
 	bssgp_vty_init();
 	gprs_llc_vty_init();
 	gprs_sndcp_vty_init();
-	sgsn_auth_init(&sgsn_inst);
+	sgsn_auth_init();
 	/* FIXME: register signal handler for SS_L_NS */
 
 	rc = sgsn_parse_config(sgsn_inst.config_file, &sgsn_inst.cfg);