gprs_ns2_fr: Avoid stringop-truncation warning

gprs_ns2_fr.c:448:2: error: ‘strncpy’ specified bound 16 equals destination size [-Werror=stringop-truncation]
  448 |  strncpy(req.ifr_name, netif, IFNAMSIZ);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Change-Id: Ied9fd1bea091075fad266258da39e674d10d4dcb
diff --git a/src/gb/gprs_ns2_fr.c b/src/gb/gprs_ns2_fr.c
index 6019302..1485961 100644
--- a/src/gb/gprs_ns2_fr.c
+++ b/src/gb/gprs_ns2_fr.c
@@ -445,7 +445,7 @@
 		return sock;
 
 	memset(&req, 0, sizeof req);
-	strncpy(req.ifr_name, netif, IFNAMSIZ);
+	OSMO_STRLCPY_ARRAY(req.ifr_name, netif);
 
 	if (up)
 		req.ifr_flags |= IFF_UP;