Use explicit parameter for sgsn_auth_init()

This is necessary to properly test ACLs in follow-up patches.

Change-Id: Ibeba371234680f33ad35afbfffce9dca185228c1
diff --git a/src/gprs/sgsn_main.c b/src/gprs/sgsn_main.c
index 1c76d6f..798e507 100644
--- a/src/gprs/sgsn_main.c
+++ b/src/gprs/sgsn_main.c
@@ -432,7 +432,7 @@
 	bssgp_vty_init();
 	gprs_llc_vty_init();
 	gprs_sndcp_vty_init();
-	sgsn_auth_init();
+	sgsn_auth_init(sgsn);
 	sgsn_cdr_init(sgsn);
 	/* FIXME: register signal handler for SS_L_NS */