use new OSMO_IMSI_BUF_SIZE

Depends: Id11ada4c96b79f7f0ad58185ab7dbf24622fb770 (libosmocore)
Change-Id: I8e8fa221e97303df3c6cce96b25d31a53f67b939
diff --git a/src/hlr_ussd.c b/src/hlr_ussd.c
index 50a0167..4024780 100644
--- a/src/hlr_ussd.c
+++ b/src/hlr_ussd.c
@@ -150,7 +150,7 @@
 	/* link us to hlr->ss_sessions */
 	struct llist_head list;
 	/* imsi of this session */
-	char imsi[GSM23003_IMSI_MAX_DIGITS+2];
+	char imsi[OSMO_IMSI_BUF_SIZE];
 	/* ID of this session (unique per IMSI) */
 	uint32_t session_id;
 	/* state of the session */