use old nvmutil for now, in lbmk

i'm trying to make nvmutil work on openbsd. the new code
in lbutils is a bit buggy, likely somewhere in mkhtemp.
i'm still debugging it.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/lib/usage.c

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: MIT
+ * Copyright (c) 2023 Riku Viitanen <riku.viitanen@protonmail.com>
+ * Copyright (c) 2026 Leah Rowe <leah@libreboot.org>
+ */
+
+#include <errno.h>
+#include <stdio.h>
+
+#include "../include/common.h"
+
+void
+usage(void)
+{
+	const char *util = getnvmprogname();
+
+	fprintf(stderr,
+	    "Modify Intel GbE NVM images e.g. set MAC\n"
+	    "USAGE:\n"
+	    "\t%s FILE dump\n"
+	    "\t%s FILE setmac [MAC]\n"
+	    "\t%s FILE swap\n"
+	    "\t%s FILE copy 0|1\n"
+	    "\t%s FILE cat\n"
+	    "\t%s FILE cat16\n"
+	    "\t%s FILE cat128\n",
+	    util, util, util, util,
+	    util, util, util);
+
+	err(EINVAL, "Too few arguments");
+}