rpcsec_gss: Use a designated initializer for rpc_gss_ops

No functional change intended.

MFC after:	1 week
Sponsored by:	The FreeBSD Foundation

sys/rpc/rpcsec_gss/rpcsec_gss.c

@@ -98,11 +98,11 @@ static void	rpc_gss_destroy(AUTH *);
 static void	rpc_gss_destroy_context(AUTH *, bool_t);
 
 static struct auth_ops rpc_gss_ops = {
-	rpc_gss_nextverf,
-	rpc_gss_marshal,
-	rpc_gss_validate,
-	rpc_gss_refresh,
-	rpc_gss_destroy,
+	.ah_nextverf =	rpc_gss_nextverf,
+	.ah_marshal =	rpc_gss_marshal,
+	.ah_validate =	rpc_gss_validate,
+	.ah_refresh =	rpc_gss_refresh,
+	.ah_destroy =	rpc_gss_destroy,
 };
 
 enum rpcsec_gss_state {